WorldWideScience

Sample records for canopy nitrogen carbon

  1. Does canopy nitrogen uptake enhance carbon sequestration by trees?

    Science.gov (United States)

    Nair, Richard K F; Perks, Micheal P; Weatherall, Andrew; Baggs, Elizabeth M; Mencuccini, Maurizio

    2016-02-01

    Temperate forest (15) N isotope trace experiments find nitrogen (N) addition-driven carbon (C) uptake is modest as little additional N is acquired by trees; however, several correlations of ambient N deposition against forest productivity imply a greater effect of atmospheric nitrogen deposition than these studies. We asked whether N deposition experiments adequately represent all processes found in ambient conditions. In particular, experiments typically apply (15) N to directly to forest floors, assuming uptake of nitrogen intercepted by canopies (CNU) is minimal. Additionally, conventional (15) N additions typically trace mineral (15) N additions rather than litter N recycling and may increase total N inputs above ambient levels. To test the importance of CNU and recycled N to tree nutrition, we conducted a mesocosm experiment, applying 54 g N/(15) N ha(-1)  yr(-1) to Sitka spruce saplings. We compared tree and soil (15) N recovery among treatments where enrichment was due to either (1) a (15) N-enriched litter layer, or mineral (15) N additions to (2) the soil or (3) the canopy. We found that 60% of (15) N applied to the canopy was recovered above ground (in needles, stem and branches) while only 21% of (15) N applied to the soil was found in these pools. (15) N recovery from litter was low and highly variable. (15) N partitioning among biomass pools and age classes also differed among treatments, with twice as much (15) N found in woody biomass when deposited on the canopy than soil. Stoichiometrically calculated N effect on C uptake from (15) N applied to the soil, scaled to real-world conditions, was 43 kg C kg N(-1) , similar to manipulation studies. The effect from the canopy treatment was 114 kg C kg N(-1) . Canopy treatments may be critical to accurately represent N deposition in the field and may address the discrepancy between manipulative and correlative studies.

  2. Elevated CO2 and nitrogen availability have interactive effects on canopy carbon gain in rice

    NARCIS (Netherlands)

    Anten, N.P.R.; Hirose, T.; Onoda, Y.; Kinugasa, T.; Kim, H.Y.; Okada, M.; Kobayashi, K.

    2004-01-01

    Here we analysed the effects of CO2 (C-a) elevation and nitrogen availability on canopy structure, leaf area index (LAI) and canopy photosynthesis of rice (Oryza sativa). Rice was grown at ambient and elevated C-a (c. 200 mumol mol(-1) above ambient, using the free-air CO2 enrichment, FACE) and at t

  3. Remote sensing of sagebrush canopy nitrogen

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    Mitchell, Jessica J.; Glenn, Nancy F.; Sankey, Temuulen T.; Derryberry, DeWayne R.; Germino, Matthew J.

    2012-01-01

    This paper presents a combination of techniques suitable for remotely sensing foliar Nitrogen (N) in semiarid shrublands – a capability that would significantly improve our limited understanding of vegetation functionality in dryland ecosystems. The ability to estimate foliar N distributions across arid and semi-arid environments could help answer process-driven questions related to topics such as controls on canopy photosynthesis, the influence of N on carbon cycling behavior, nutrient pulse dynamics, and post-fire recovery. Our study determined that further exploration into estimating sagebrush canopy N concentrations from an airborne platform is warranted, despite remote sensing challenges inherent to open canopy systems. Hyperspectral data transformed using standard derivative analysis were capable of quantifying sagebrush canopy N concentrations using partial least squares (PLS) regression with an R2 value of 0.72 and an R2 predicted value of 0.42 (n = 35). Subsetting the dataset to minimize the influence of bare ground (n = 19) increased R2 to 0.95 (R2 predicted = 0.56). Ground-based estimates of canopy N using leaf mass per unit area measurements (LMA) yielded consistently better model fits than ground-based estimates of canopy N using cover and height measurements. The LMA approach is likely a method that could be extended to other semiarid shrublands. Overall, the results of this study are encouraging for future landscape scale N estimates and represent an important step in addressing the confounding influence of bare ground, which we found to be a major influence on predictions of sagebrush canopy N from an airborne platform.

  4. Hyperspectral canopy reflectance as a predictor for root concentrations of nitrogen and carbon in native and non native grass species

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    Land managers, scientists, and crop professionals need real-time, inexpensive, and labor-saving methods to determine below-ground biomass and potential carbon (C) and nitrogen (N) inputs of that biomass. Remote sensing is a non-destructive tool that monitors vigor of vegetation and has been used t...

  5. Optimality of nitrogen distribution among leaves in plant canopies.

    Science.gov (United States)

    Hikosaka, Kouki

    2016-05-01

    The vertical gradient of the leaf nitrogen content in a plant canopy is one of the determinants of vegetation productivity. The ecological significance of the nitrogen distribution in plant canopies has been discussed in relation to its optimality; nitrogen distribution in actual plant canopies is close to but always less steep than the optimal distribution that maximizes canopy photosynthesis. In this paper, I review the optimality of nitrogen distribution within canopies focusing on recent advancements. Although the optimal nitrogen distribution has been believed to be proportional to the light gradient in the canopy, this rule holds only when diffuse light is considered; the optimal distribution is steeper when the direct light is considered. A recent meta-analysis has shown that the nitrogen gradient is similar between herbaceous and tree canopies when it is expressed as the function of the light gradient. Various hypotheses have been proposed to explain why nitrogen distribution is suboptimal. However, hypotheses explain patterns observed in some specific stands but not in others; there seems to be no general hypothesis that can explain the nitrogen distributions under different conditions. Therefore, how the nitrogen distribution in canopies is determined remains open for future studies; its understanding should contribute to the correct prediction and improvement of plant productivity under changing environments.

  6. Advances in Nitrogen Loss Leached by Precipitation from Plant Canopy

    Institute of Scientific and Technical Information of China (English)

    LI Shi-qing; JI Chun-rong; FANG Ya-ning; CHEN Xiao-li; LI Sheng-xiu

    2008-01-01

    Function of canopy in changing nutrient cycle and flux is one of the focuses in recent years. On the basis of comprehensively appraising published research, we analyzed the nitrogen loss leaching from plant canopy and several factors which affected it. We pointed out the disadvantages of the published researches and the key issues that ought to be solved: (1) The menstruation need to be advanced, and the research should be carried out on nitrogen loss leaching from the canopy of the field plant. (2) If the nitrogen is leached from the plant canopy, the research on the type of nitrogen loss should be carried out, and the nitrogen use efficiency of different varieties should be dealt on a research perspective with regard to the nitrogen leaching. (3) The research should be conducted on the mechanism and pathway, and the progress of nitrogen leaching; and the factors affecting nitrogen leaching should be included in the research, such as the leaf area of different growth stages, stomata densities, stomata conductance, and the apparent free space, which are beneficial to explain the mechanism of nitrogen leaching from the plant canopy.

  7. Hyperspectral canopy reflectance as a predictor for root concentrations of nitrogen and carbon in native and non-native grass species

    Science.gov (United States)

    Land managers, scientists or crop professionals need a real-time method to determine below-ground biomass and potential carbon (C) and nitrogen (N) inputs from that biomass without excessive labor. Remote sensing is a non-destructive assessment tool that monitors vigor of vegetation and is used to a...

  8. Canopy foliar nitrogen retrieved from airborne hyperspectral imagery by correcting for canopy structure effects

    Science.gov (United States)

    Wang, Zhihui; Skidmore, Andrew K.; Wang, Tiejun; Darvishzadeh, Roshanak; Heiden, Uta; Heurich, Marco; Latifi, Hooman; Hearne, John

    2017-02-01

    A statistical relationship between canopy mass-based foliar nitrogen concentration (%N) and canopy bidirectional reflectance factor (BRF) has been repeatedly demonstrated. However, the interaction between leaf properties and canopy structure confounds the estimation of foliar nitrogen. The canopy scattering coefficient (the ratio of BRF and the directional area scattering factor, DASF) has recently been suggested for estimating %N as it suppresses the canopy structural effects on BRF. However, estimation of %N using the scattering coefficient has not yet been investigated for longer spectral wavelengths (>855 nm). We retrieved the canopy scattering coefficient for wavelengths between 400 and 2500 nm from airborne hyperspectral imagery, and then applied a continuous wavelet analysis (CWA) to the scattering coefficient in order to estimate %N. Predictions of %N were also made using partial least squares regression (PLSR). We found that %N can be accurately retrieved using CWA (R2 = 0.65, RMSE = 0.33) when four wavelet features are combined, with CWA yielding a more accurate estimation than PLSR (R2 = 0.47, RMSE = 0.41). We also found that the wavelet features most sensitive to %N variation in the visible region relate to chlorophyll absorption, while wavelet features in the shortwave infrared regions relate to protein and dry matter absorption. Our results confirm that %N can be retrieved using the scattering coefficient after correcting for canopy structural effect. With the aid of high-fidelity airborne or upcoming space-borne hyperspectral imagery, large-scale foliar nitrogen maps can be generated to improve the modeling of ecosystem processes as well as ecosystem-climate feedbacks.

  9. Spatial variation in atmospheric nitrogen deposition on low canopy vegetation

    Energy Technology Data Exchange (ETDEWEB)

    Verhagen, Rene [Community and Conservation Ecology Group, University of Groningen, P.O. Box 14, 9750 AA Haren (Netherlands); Diggelen, Rudy van [Community and Conservation Ecology Group, University of Groningen, P.O. Box 14, 9750 AA Haren (Netherlands)]. E-mail: r.van.diggelen@rug.nl

    2006-12-15

    Current knowledge about the spatial variation of atmospheric nitrogen deposition on a local scale is limited, especially for vegetation with a low canopy. We measured nitrogen deposition on artificial vegetation at variable distances of local nitrogen emitting sources in three nature reserves in the Netherlands, differing in the intensity of agricultural practices in the surroundings. In the nature reserve located in the most intensive agricultural region nitrogen deposition decreased with increasing distance to the local farms, until at a distance of 1500 m from the local nitrogen emitting sources the background level of 15 kg N ha{sup -1} yr{sup -1} was reached. No such trend was observed in the other two reserves. Interception was considerably lower than in woodlands and hence affected areas were larger. The results are discussed in relation to the prospects for the conservation or restoration of endangered vegetation types of nutrient-poor soil conditions. - Areas with low canopy vegetation are affected over much larger distances by nitrogen deposition than woodlands.

  10. Estimating Canopy Nitrogen Concentration in Sugarcane Using Field Imaging Spectroscopy

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    Marc Souris

    2012-06-01

    Full Text Available The retrieval of nutrient concentration in sugarcane through hyperspectral remote sensing is widely known to be affected by canopy architecture. The goal of this research was to develop an estimation model that could explain the nitrogen variations in sugarcane with combined cultivars. Reflectance spectra were measured over the sugarcane canopy using a field spectroradiometer. The models were calibrated by a vegetation index and multiple linear regression. The original reflectance was transformed into a First-Derivative Spectrum (FDS and two absorption features. The results indicated that the sensitive spectral wavelengths for quantifying nitrogen content existed mainly in the visible, red edge and far near-infrared regions of the electromagnetic spectrum. Normalized Differential Index (NDI based on FDS(750/700 and Ratio Spectral Index (RVI based on FDS(724/700 are best suited for characterizing the nitrogen concentration. The modified estimation model, generated by the Stepwise Multiple Linear Regression (SMLR technique from FDS centered at 410, 426, 720, 754, and 1,216 nm, yielded the highest correlation coefficient value of 0.86 and Root Mean Square Error of the Estimate (RMSE value of 0.033%N (n = 90 with nitrogen concentration in sugarcane. The results of this research demonstrated that the estimation model developed by SMLR yielded a higher correlation coefficient with nitrogen content than the model computed by narrow vegetation indices. The strong correlation between measured and estimated nitrogen concentration indicated that the methods proposed in this study could be used for the reliable diagnosis of nitrogen quantity in sugarcane. Finally, the success of the field spectroscopy used for estimating the nutrient quality of sugarcane allowed an additional experiment using the polar orbiting hyperspectral data for the timely determination of crop nutrient status in rangelands without any requirement of prior

  11. Nitrogen Availability and Forest Canopy Albedo from Leaf to Regional Scales

    Science.gov (United States)

    Ollinger, S. V.; Plourde, L. C.; Martin, M.; Wicklein, H. F.; Haddad, D. M.; Richardson, A. D.; Hollinger, D.

    2009-12-01

    CO2 uptake capacity in temperate and boreal forests has been shown to scale directly with whole-canopy nitrogen concentrations, mirroring a leaf-level trend that has been observed for woody plants worldwide. Recent work has also demonstrated that both CO2 uptake capacity and canopy %N are strongly and positively correlated with shortwave surface albedo. This suggests that variation in nitrogen availability may play an additional, and previously overlooked, role in the climate system via its influence on surface energy exchange as well as via its better-known influence on carbon assimilation. Thus far, the carbon-nitrogen-albedo relationship has been demonstrated at relatively coarse spatial scales that cover broad gradients in climate and forest type. It is unclear whether similar trends occur within local landscapes and within ecosystems other than forests. It is also unclear whether N deposition and N fertilization can cause a shift in albedo stemming from changes in foliar %N. Examining finer-scale patterns in the N-albedo relationship is necessary before we can establish the generality of the observed trends and understand their implications for carbon-nutrient-climate interactions. Here, we expand on the C-N-albedo relationship in several important ways: (1) using fine-scale remote sensing data from the U.S. and Canada, we examined albedo in relation to foliar N and canopy structure at local scales for several well characterized landscapes; (2) we examined changes in both foliar N and albedo along a regional-scale nitrogen deposition gradient; (3) we examined leaf-level changes in %N and albedo in response to experimental N additions, and (4) we conducted a global synthesis of data from FLUXNET to examine the C-N-albedo relationship over a broader range of ecosystems. Results are discussed in the context of improving our understanding of interactions between terrestrial biogeochemistry and climate.

  12. CAN Canopy Addition of Nitrogen Better Illustrate the Effect of Atmospheric Nitrogen Deposition on Forest Ecosystem?

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    Zhang, Wei; Shen, Weijun; Zhu, Shidan; Wan, Shiqiang; Luo, Yiqi; Yan, Junhua; Wang, Keya; Liu, Lei; Dai, Huitang; Li, Peixue; Dai, Keyuan; Zhang, Weixin; Liu, Zhanfeng; Wang, Faming; Kuang, Yuanwen; Li, Zhian; Lin, Yongbiao; Rao, Xingquan; Li, Jiong; Zou, Bi; Cai, Xian; Mo, Jiangming; Zhao, Ping; Ye, Qing; Huang, Jianguo; Fu, Shenglei

    2015-06-01

    Increasing atmospheric nitrogen (N) deposition could profoundly impact community structure and ecosystem functions in forests. However, conventional experiments with understory addition of N (UAN) largely neglect canopy-associated biota and processes and therefore may not realistically simulate atmospheric N deposition to generate reliable impacts on forest ecosystems. Here we, for the first time, designed a novel experiment with canopy addition of N (CAN) vs. UAN and reviewed the merits and pitfalls of the two approaches. The following hypotheses will be tested: i) UAN overestimates the N addition effects on understory and soil processes but underestimates those on canopy-associated biota and processes, ii) with low-level N addition, CAN favors canopy tree species and canopy-dwelling biota and promotes the detritus food web, and iii) with high-level N addition, CAN suppresses canopy tree species and other biota and favors rhizosphere food web. As a long-term comprehensive program, this experiment will provide opportunities for multidisciplinary collaborations, including biogeochemistry, microbiology, zoology, and plant science to examine forest ecosystem responses to atmospheric N deposition.

  13. Integrating soil information into canopy sensor algorithms for improved corn nitrogen rate recommendation

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    Crop canopy sensors have proven effective at determining site-specific nitrogen (N) needs, but several Midwest states use different algorithms to predict site-specific N need. The objective of this research was to determine if soil information can be used to improve the Missouri canopy sensor algori...

  14. Dynamics of vertical leaf nitrogen distribution in a vegetative wheat canopy Impact on canopy photosynthesis

    NARCIS (Netherlands)

    Dreccer, M.F.; Oijen, van M.; Schapendonk, A.H.C.M.; Pot, C.S.; Rabbinge, R.

    2000-01-01

    The development of vertical canopy gradients of leaf N has been regarded as an adaptation to the light gradient that helps to maximize canopy photosynthesis. In this study we report the dynamics of vertical leaf N distribution during vegetative growth of wheat in response to changes in N availabilit

  15. Atmospheric Nitrogen Deposition at a Conifer Forest: Canopy Nitrogen Uptake and Photosynthesis

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    Tomaszewski, T.; Sievering, H.

    2006-12-01

    Atmospheric nitrogen (N) deposition is known to impact forests in a variety of ways ranging from increased growth and photosynthesis to needle necrosis. More than half of the growing-season N deposition flux at the Niwot Ridge Long-Term Ecological Research site's subalpine forest (Niwot Forest) is of anthropogenic origin. N fertilization studies investigating forest responses to increased N deposition have primarily dealt with deposition loading to the soil. However, some studies indicate that forest canopies (especially conifer forest canopies) retain a substantial portion of atmospherically-deposited N before this N reaches the soil in throughfall solutions. In the present study, canopy N uptake (CNU) and the influence of CNU on photosynthesis are investigated. At the Niwot Forest, growing-season throughfall fluxes of ammonium (NH4+) and nitrate (NO3-) are markedly lower (~70% lower) than fluxes in wet plus dry deposition flux, indicating the forest canopy is taking up atmospherically-deposited N. This uptake was found to be driven by diffusion of NH4+ and NO3- into canopy tissues. Although the canopy is taking up atmospherically-deposited N, spruce foliar N content is still relatively low at the Niwot Forest. This low foliar N content contributes to low rates of light-saturated photosynthesis and maximum carboxylation (initial rate of CO2 reduction by RUBISCO). Further, a strong linear dependence of maximum carboxylation on needle N content was found and N solutions that had been directly applied to foliage at Niwot Forest spruce branches induced a 12% greater photosynthetic efficiency (i.e., proportion of absorbed light utilized by photosynthesis). The low foliar N content and dependence of photosynthetic parameters on foliar N content show that the Niwot Forest has yet to reach a state of N saturation. Noting the Niwot Forest has one of the largest N deposition fluxes in the Rockies, our CNU and photosynthetic parameter results characterizing pre

  16. Vegetation Indices for Mapping Canopy Foliar Nitrogen in a Mixed Temperate Forest

    Directory of Open Access Journals (Sweden)

    Zhihui Wang

    2016-06-01

    Full Text Available Hyperspectral remote sensing serves as an effective tool for estimating foliar nitrogen using a variety of techniques. Vegetation indices (VIs are a simple means of retrieving foliar nitrogen. Despite their popularity, few studies have been conducted to examine the utility of VIs for mapping canopy foliar nitrogen in a mixed forest context. In this study, we assessed the performance of 32 vegetation indices derived from HySpex airborne hyperspectral images for estimating canopy mass-based foliar nitrogen concentration (%N in the Bavarian Forest National Park. The partial least squares regression (PLSR was performed for comparison. These vegetation indices were classified into three categories that are mostly correlated to nitrogen, chlorophyll, and structural properties such as leaf area index (LAI. %N was destructively measured in 26 broadleaf, needle leaf, and mixed stand plots to represent the different species and canopy structure. The canopy foliar %N is defined as the plot-level mean foliar %N of all species weighted by species canopy foliar mass fraction. Our results showed that the variance of canopy foliar %N is mainly explained by functional type and species composition. The normalized difference nitrogen index (NDNI produced the most accurate estimation of %N (R2CV = 0.79, RMSECV = 0.26. A comparable estimation of %N was obtained by the chlorophyll index Boochs2 (R2CV = 0.76, RMSECV = 0.27. In addition, the mean NIR reflectance (800–850 nm, representing canopy structural properties, also achieved a good accuracy in %N estimation (R2CV = 0.73, RMSECV = 0.30. The PLSR model provided a less accurate estimation of %N (R2CV = 0.69, RMSECV = 0.32. We argue that the good performance of all three categories of vegetation indices in %N estimation can be attributed to the synergy among plant traits (i.e., canopy structure, leaf chemical and optical properties while these traits may converge across plant species for evolutionary reasons. Our

  17. Nitrogen doping in carbon nanotubes.

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    Ewels, C P; Glerup, M

    2005-09-01

    Nitrogen doping of single and multi-walled carbon nanotubes is of great interest both fundamentally, to explore the effect of dopants on quasi-1D electrical conductors, and for applications such as field emission tips, lithium storage, composites and nanoelectronic devices. We present an extensive review of the current state of the art in nitrogen doping of carbon nanotubes, including synthesis techniques, and comparison with nitrogen doped carbon thin films and azofullerenes. Nitrogen doping significantly alters nanotube morphology, leading to compartmentalised 'bamboo' nanotube structures. We review spectroscopic studies of nitrogen dopants using techniques such as X-ray photoemission spectroscopy, electron energy loss spectroscopy and Raman studies, and associated theoretical models. We discuss the role of nanotube curvature and chirality (notably whether the nanotubes are metallic or semiconducting), and the effect of doping on nanotube surface chemistry. Finally we review the effect of nitrogen on the transport properties of carbon nanotubes, notably its ability to induce negative differential resistance in semiconducting tubes.

  18. [Active crop canopy sensor-based nitrogen diagnosis for potato].

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    Yu, Jing; Li, Fei; Qin, Yong-Lin; Fan, Ming-Shou

    2013-11-01

    In the present study, two potato experiments involving different N rates in 2011 were conducted in Wuchuan County and Linxi County, Inner Mongolia. Normalized difference vegetation index (NDVI) was collected by an active GreenSeeker crop canopy sensor to estimate N status of potato. The results show that the NDVI readings were poorly correlated with N nutrient indicators of potato at vegetative Growth stage due to the influence of soil background. With the advance of growth stages, NDVI values were exponentially related to plant N uptake (R2 = 0.665) before tuber bulking stage and were linearly related to plant N concentration (R2 = 0.699) when plant fully covered soil. In conclusion, GreenSeeker active crop sensor is a promising tool to estimate N status for potato plants. The findings from this study may be useful for developing N recommendation method based on active crop canopy sensor.

  19. Integrating soil and weather information into canopy sensor algorithms for improved corn nitrogen rate recommendation

    Science.gov (United States)

    Corn production can be often limited by the loss of nitrogen (N) due to leaching, volatilization and denitrification. The use of canopy sensors for making in-season N fertilizer applications has been proven effective in matching plant N requirements with periods of rapid N uptake (V7-V11), reducing ...

  20. Modeling forest development after fire disturbance: Climate, soil organic layer, and nitrogen jointly affect forest canopy species and long-term ecosystem carbon accumulation in the North American boreal forest

    Science.gov (United States)

    Trugman, A. T.; Fenton, N.; Bergeron, Y.; Xu, X.; Welp, L.; Medvigy, D.

    2015-12-01

    Soil organic layer dynamics strongly affect boreal forest development after fire. Field studies show that soil organic layer thickness exerts a species-specific control on propagule establishment in the North American boreal forest. On organic soils thicker than a few centimeters, all propagules are less able to recruit, but broadleaf trees recruit less effectively than needleleaf trees. In turn, forest growth controls organic layer accumulation through modulating litter input and litter quality. These dynamics have not been fully incorporated into models, but may be essential for accurate projections of ecosystem carbon storage. Here, we develop a data-constrained model for understanding boreal forest development after fire. We update the ED2 model to include new aspen and black spruce species-types, species-specific propagule survivorship dependent on soil organic layer depth, species-specific litter decay rates, dynamically accumulating moss and soil organic layers, and nitrogen fixation by cyanobacteria associated with moss. The model is validated against diverse observations ranging from monthly to centennial timescales and spanning a climate gradient in Alaska, central Canada, and Quebec. We then quantify differences in forest development that result from changes in organic layer accumulation, temperature, and nitrogen. We find that (1) the model accurately reproduces a range of observations throughout the North American boreal forest; (2) the presence of a thick organic layer results in decreased decomposition and decreased aboveground productivity, effects that can increase or decrease ecosystem carbon uptake depending on location-specific attributes; (3) with a mean warming of 4°C, some forests switch from undergoing succession to needleleaf forests to recruiting multiple cohorts of broadleaf trees, decreasing ecosystem accumulation by ~30% after 300 years; (4) the availability of nitrogen regulates successional dynamics such than broadleaf species are

  1. Nitrogen-doped hydrothermal carbons

    Energy Technology Data Exchange (ETDEWEB)

    Titirici, Maria-Magdalena; White, Robin J. [Max-Planck-Institute of Colloids and Interfaces, Potsdam (Germany). Dept. of Colloid Chemistry; Zhao, Li [Max-Planck-Institute of Colloids and Interfaces, Potsdam (Germany). Dept. of Colloid Chemistry; National Center for Nanoscience and Technology, Beijing (China)

    2012-07-01

    Nitrogen doped carbon materials are now playing an important role in cutting edge innovations for energy conversion and storage technologies such as supercapacitors and proton exchange membrane fuel cells as well as in catalytic applications, adsorption and CO{sub 2} capture. The production of such materials using benign aqueous based processes, mild temperatures and renewable precursors is of great promise in addressing growing environmental concerns for cleaner power sources at a time of increasing global demand for energy. In this perspective, we show that nitrogen doped carbons prepared using sustainable processes such as ''Hydrothermal Carbonisation'' has advantages in many applications over the conventional carbons. We also summarize an array of synthetic strategies used to create such nitrogen doped carbons, and discuss the application of these novel materials. (orig.)

  2. Estimating the Total Nitrogen Concentration of Reed Canopy with Hyperspectral Measurements Considering a Non-Uniform Vertical Nitrogen Distribution

    Directory of Open Access Journals (Sweden)

    Juhua Luo

    2016-09-01

    Full Text Available The total nitrogen concentration (NC, g/100 g of wetland plants is an important parameter to estimate the wetland health status and to calculate the nitrogen storage of wetland plants. Remote sensing has been widely used to estimate biophysical, physiological, and biochemical parameters of plants. However, current studies place little emphasis on NC estimations by only taking nitrogen’s vertical distribution into consideration, resulting in limited accuracy and decreased practical value of the results. The main goal of this study is to develop a model, considering a non-uniform vertical nitrogen distribution to estimate the total NC of the reed canopy, which is one of the wetland’s dominant species, using hyperspectral data. Sixty quadrats were selected and measured based on an experimental design that considered vertical layer divisions within the reed canopy. Using the measured NCs of different leaf layers and corresponding spectra from the quadrats, the results indicated that the vertical distribution law of the NC was distinct, presenting an initial increase and subsequent decrease from the top layer to the bottom layer. The spectral indices MCARI/MTVI2, TCARI/OSAVI, MMTCI, DCNI, and PPR/NDVI had high R2 values when related to NC (R2 > 0.5 and low R2 when related to LAI (R2 < 0.2 and could minimize the influence of LAI and increase the sensitivity to changes in NC of the reed canopy. The relative variation rates (Rv, % of these spectral indices, calculated from each quadrat, also indicated that the top three layers of the reed canopy were an effective depth to estimate NCs using hyperspectral data. A model was developed to estimate the total NC of the whole reed canopy based on PPR/DNVI with R2 = 0.88 and RMSE = 0.37%. The model, which considered the vertical distribution patterns of the NC and the effective canopy layers, has demonstrated great potential to estimate the total NC of the whole reed canopy.

  3. Frankia and Alnus rubra canopy roots: an assessment of genetic diversity, propagule availability, and effects on soil nitrogen.

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    Kennedy, Peter G; Schouboe, Jesse L; Rogers, Rachel H; Weber, Marjorie G; Nadkarni, Nalini M

    2010-02-01

    The ecological importance of microbial symbioses in terrestrial soils is widely recognized, but their role in soils that accumulate in forest canopies is almost entirely unknown. To address this gap, this study investigated the Frankia-Alnus rubra symbiosis in canopy and forest floor roots at Olympic National Park, WA, USA. Sixteen mature A. rubra trees were surveyed and Frankia genetic diversity in canopy and forest floor nodules was assessed with sequence-based nifH analyses. A seedling bioassay experiment was conducted to determine Frankia propagule availability in canopy and forest floor soils. Total soil nitrogen from both environments was also quantified. Nodules were present in the canopies of nine of the 16 trees sampled. Across the study area, Frankia canopy and forest floor assemblages were similar, with both habitats containing the same two genotypes. The composition of forest floor and canopy genotypes on the same tree was not always identical, however, suggesting that dispersal was not a strictly local phenomenon. Frankia seedling colonization was similar in canopy soils regardless of the presence of nodules as well as in forest floor soils, indicating that dispersal was not likely to be a major limiting factor. The total soil nitrogen of canopy soils was higher than that of forest floor soils, but the presence of Frankia nodules in canopy soils did not significantly alter soil nitrogen levels. Overall, this study indicates that the Frankia-A. rubra symbiosis is similar in canopy and forest floor environments. Because canopy roots are exposed to different environmental conditions within very small spatial areas and because those areas can be easily manipulated (e.g., fertilizer or watering treatments), they present microbial ecologists with a unique arena to examine root-microbe interactions.

  4. Hyperspectral assessment of nitrogen nutrition for winter wheat canopy using continuum-removed method

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    Zhang, Xuehong; Shen, Runping; Zhu, Shanyou

    2009-10-01

    The hyperspectral reflectance of canopy of winter wheat and data of leaf nitrogen accumulation (LNA) were acquired in primary growth stages under different nitrogen levels in order to monitor winter wheat status and diagnose nitrogen using remote sensing method. A new method was developed to estimate the nitrogen nutrition of winter wheat using continuum-removed method, which generally used in spectra analysis on rock and mineral. The continuum-removed method was effectively used to magnify the object spectral absorption features, and it could be convenient to extract the spectral absorption features. Based on the continuum-removed treatment and the correlation between absorption feature parameters and LNA, results show that LNA increased with increasing the nitrogen fertilization. LNA increased from the erecting stage to the booting stage and decreases from the booting to the heading stage under all nitrogen levels. It is the VNIR regions that were sensitive to LNA. By continuum removal operation, it can be found that the method magnify the subtle difference in spectral absorption characteristics arise from the nitrogen stress on winter wheat. At all stages, total area of absorption peak, left area of absorption peak, right area of absorption peak increased with increasing the nitrogen fertilization, whereas the normalized maximal absorption depth by area decreased. The correlation analysis indicated that all the absorption characteristics parameters of continuum-removed spectra highly correlated with LNA, and the correlation relationship of the whole growth cycle was stronger than that of any single growth stage. But the booting stage is the best at the several single growth stages and the NMAD is the best absorption parameter to monitoring the nitrogen of winter wheat canopy. The range 550 nm to 760 nm are the feature bands for extracting nitrogen information of canopy. The regression analysis on the whole growth period showed that the all regression models

  5. Forest defoliator pests alter carbon and nitrogen cycles

    Science.gov (United States)

    Grüning, Maren; Simon, Judy; Reinhardt, Annett-Barbara; Lamersdorf, Norbert; Thies, Carsten

    2016-01-01

    Climate change may foster pest epidemics in forests, and thereby the fluxes of elements that are indicators of ecosystem functioning. We examined compounds of carbon (C) and nitrogen (N) in insect faeces, leaf litter, throughfall and analysed the soils of deciduous oak forests (Quercus petraea L.) that were heavily infested by the leaf herbivores winter moth (Operophtera brumata L.) and mottled umber (Erannis defoliaria L.). In infested forests, total net canopy-to-soil fluxes of C and N deriving from insect faeces, leaf litter and throughfall were 30- and 18-fold higher compared with uninfested oak forests, with 4333 kg C ha−1 and 319 kg N ha−1, respectively, during a pest outbreak over 3 years. In infested forests, C and N levels in soil solutions were enhanced and C/N ratios in humus layers were reduced indicating an extended canopy-to-soil element pathway compared with the non-infested forests. In a microcosm incubation experiment, soil treatments with insect faeces showed 16-fold higher fluxes of carbon dioxide and 10-fold higher fluxes of dissolved organic carbon compared with soil treatments without added insect faeces (control). Thus, the deposition of high rates of nitrogen and rapidly decomposable carbon compounds in the course of forest pest epidemics appears to stimulate soil microbial activity (i.e. heterotrophic respiration), and therefore, may represent an important mechanism by which climate change can initiate a carbon cycle feedback. PMID:27853551

  6. Remote estimation of canopy nitrogen content in winter wheat using airborne hyperspectral reflectance measurements

    Science.gov (United States)

    Zhou, Xianfeng; Huang, Wenjiang; Kong, Weiping; Ye, Huichun; Luo, Juhua; Chen, Pengfei

    2016-11-01

    Timely and accurate assessment of canopy nitrogen content (CNC) provides valuable insight into rapid and real-time nitrogen status monitoring in crops. A semi-empirical approach based on spectral index was extensively used for nitrogen content estimation. However, in many cases, due to specific vegetation types or local conditions, the applicability and robustness of established spectral indices for nitrogen retrieval were limited. The objective of this study was to investigate the optimal spectral index for winter wheat (Triticum aestivum L.) CNC estimation using Pushbroom Hyperspectral Imager (PHI) airborne hyperspectral data. Data collected from two different field experiments that were conducted during the major growth stages of winter wheat in 2002 and 2003 were used. Our results showed that a significant linear relationship existed between nitrogen and chlorophyll content at the canopy level, and it was not affected by cultivars, growing conditions and nutritional status of winter wheat. Nevertheless, it varied with growth stages. Periods around heading stage mainly worsened the relationship and CNC estimation, and CNC assessment for growth stages before and after heading could improve CNC retrieval accuracy to some extent. CNC assessment with PHI airborne hyperspectra suggested that spectral indices based on red-edge band including narrowband and broadband CIred-edge, NDVI-like and ND705 showed convincing results in CNC retrieval. NDVI-like and ND705 were sensitive to detect CNC changes less than 5 g/m2, narrowband and broadband CIred-edge were sensitive to a wide range of CNC variations. Further evaluation of CNC retrieval using field measured hyperspectra indicated that NDVI-like was robust and exhibited the highest accuracy in CNC assessment, and spectral indices (CIred-edge and CIgreen) that established on narrow or broad bands showed no obvious difference in CNC assessment. Overall, our study suggested that NDVI-like was the optimal indicator for winter

  7. Canopy carbon budget of Siebold's beech (Fagus crenata) sapling under free air ozone exposure.

    Science.gov (United States)

    Watanabe, Makoto; Hoshika, Yasutomo; Inada, Naoki; Koike, Takayoshi

    2014-01-01

    To determine the effects of ozone (O3) on the canopy carbon budget, we investigated photosynthesis and respiration of leaves of Siebold's beech saplings under free air O3 exposure (60 nmol mol(-1), during daytime) in relation to the within-canopy light gradient; we then calculated the canopy-level photosynthetic carbon gain (PCG) and respiratory carbon loss (RCL) using a canopy photosynthesis model. Susceptibilities of photosynthesis and respiration to O3 were greater in leaves of upper canopy than in the lower canopy. The canopy net carbon gain (NCG) was reduced by O3 by 12.4% during one growing season. The increased RCL was the main factor for the O3-induced reduction in NCG in late summer, while contributions of the reduced PCG and the increased RCL to the NCG were almost the same in autumn. These results indicate contributions of changes in PCG and RCL under O3 to NCG were different between seasons.

  8. High-Resolution Forest Canopy Height Estimation in an African Blue Carbon Ecosystem

    Science.gov (United States)

    Lagomasino, David; Fatoyinbo, Temilola; Lee, Seung-Kuk; Simard, Marc

    2015-01-01

    Mangrove forests are one of the most productive and carbon dense ecosystems that are only found at tidally inundated coastal areas. Forest canopy height is an important measure for modeling carbon and biomass dynamics, as well as land cover change. By taking advantage of the flat terrain and dense canopy cover, the present study derived digital surface models (DSMs) using stereophotogrammetric techniques on high-resolution spaceborne imagery (HRSI) for southern Mozambique. A mean-weighted ground surface elevation factor was subtracted from the HRSI DSM to accurately estimate the canopy height in mangrove forests in southern Mozambique. The mean and H100 tree height measured in both the field and with the digital canopy model provided the most accurate results with a vertical error of 1.18-1.84 m, respectively. Distinct patterns were identified in the HRSI canopy height map that could not be discerned from coarse shuttle radar topography mission canopy maps even though the mode and distribution of canopy heights were similar over the same area. Through further investigation, HRSI DSMs have the potential of providing a new type of three-dimensional dataset that could serve as calibration/validation data for other DSMs generated from spaceborne datasets with much larger global coverage. HSRI DSMs could be used in lieu of Lidar acquisitions for canopy height and forest biomass estimation, and be combined with passive optical data to improve land cover classifications.

  9. Nitrogen cycling in canopy soils of tropical montane forests responds rapidly to indirect N and P fertilization.

    Science.gov (United States)

    Matson, Amanda L; Corre, Marife D; Veldkamp, Edzo

    2014-12-01

    Although the canopy can play an important role in forest nutrient cycles, canopy-based processes are often overlooked in studies on nutrient deposition. In areas of nitrogen (N) and phosphorus (P) deposition, canopy soils may retain a significant proportion of atmospheric inputs, and also receive indirect enrichment through root uptake followed by throughfall or recycling of plant litter in the canopy. We measured net and gross rates of N cycling in canopy soils of tropical montane forests along an elevation gradient and assessed indirect effects of elevated nutrient inputs to the forest floor. Net N cycling rates were measured using the buried bag method. Gross N cycling rates were measured using (15) N pool dilution techniques. Measurements took place in the field, in the wet and dry season, using intact cores of canopy soil from three elevations (1000, 2000 and 3000 m). The forest floor had been fertilized biannually with moderate amounts of N and P for 4 years; treatments included control, N, P, and N + P. In control plots, gross rates of NH4 (+) transformations decreased with increasing elevation; gross rates of NO3 (-) transformations did not exhibit a clear elevation trend, but were significantly affected by season. Nutrient-addition effects were different at each elevation, but combined N + P generally increased N cycling rates at all elevations. Results showed that canopy soils could be a significant N source for epiphytes as well as contributing up to 23% of total (canopy + forest floor) mineral N production in our forests. In contrast to theories that canopy soils are decoupled from nutrient cycling in forest floor soil, N cycling in our canopy soils was sensitive to slight changes in forest floor nutrient availability. Long-term atmospheric N and P deposition may lead to increased N cycling, but also increased mineral N losses from the canopy soil system.

  10. Changes in leaf area, nitrogen content and canopy photosynthesis in soybean exposed to an ozone concentration gradient.

    Science.gov (United States)

    Oikawa, Shimpei; Ainsworth, Elizabeth A

    2016-08-01

    Influences of ozone (O3) on light-saturated rates of photosynthesis in crop leaves have been well documented. To increase our understanding of O3 effects on individual- or stand level productivity, a mechanistic understanding of factors determining canopy photosynthesis is necessary. We used a canopy model to scale photosynthesis from leaf to canopy, and analyzed the importance of canopy structural and leaf ecophysiological characteristics in determining canopy photosynthesis in soybean stands exposed to 9 concentrations of [O3] (37-116 ppb; 9-h mean). Light intensity and N content peaked in upper canopy layers, and sharply decreased through the lower canopy. Plant leaf area decreased with increasing [O3] allowing for greater light intensity to reach lower canopy levels. At the leaf level, light-saturated photosynthesis decreased and dark respiration increased with increasing [O3]. These data were used to calculate daily net canopy photosynthesis (Pc). Pc decreased with increasing [O3] with an average decrease of 10% for an increase in [O3] of 10 ppb, and which was similar to changes in above-ground dry mass production of the stands. Absolute daily net photosynthesis of lower layers was very low and thus the decrease in photosynthesis in the lower canopy caused by elevated [O3] had only minor significance for total canopy photosynthesis. Sensitivity analyses revealed that the decrease in Pc was associated with changes in leaf ecophysiology but not with decrease in leaf area. The soybean stands were very crowded, the leaves were highly mutually shaded, and sufficient light for positive carbon balance did not penetrate to lower canopy leaves, even under elevated [O3].

  11. Effects of nitrogen nutrition on the growth, yield and reflectance characteristics of corn canopies. [Purdue Agronomy Farm, Indiana

    Science.gov (United States)

    Bauer, M. E. (Principal Investigator); Walburg, G.; Daughtry, C. S. T.

    1981-01-01

    Spectral and agronomic measurements were collected from corn (Zea mays L.) canopies under four nitrogen treatment levels (0, 67, 134, and 202 kg/ha) on 11 dates during 1978 and 12 dates during 1979. Data were analyzed to determine the relationship between the spectral responses of canopies and their argonomic characteristics as well as the spectral separability of the four treatments. Red reflectance was increased, while the near infrared reflectance was decreased for canopies under nitrogen deprivation. Spectral differences between treatments were seen throughout each growing season. The near infrared/red reflectance ratio increased spectral treatment differences over those shown by single band reflectance measures. Of the spectral variables examined, the near infrared/red reflectance ratio most effectively separated the treatments. Differences in spectral response between treatments were attributed to varying soil cover, leaf area index, and leaf pigmentation values, all of which changed with N treatment.

  12. Sensitivity of simulated terrestrial carbon assimilation and canopy transpiration to different stomatal conductance and carbon assimilation schemes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Haishan [Nanjing University of Information Science and Technology, Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing (China); Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States); Dickinson, Robert E. [Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States); The University of Texas at Austin, Department of Geological Sciences, Austin, TX (United States); Dai, Yongjiu [Beijing Normal University, State Key Laboratory of Earth Surface Processes and Resource Ecology, School of Global Change and Earth System Science, Beijing (China); Zhou, Liming [Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States)

    2011-03-15

    Accurate simulations of terrestrial carbon assimilation and canopy transpiration are needed for both climate modeling and vegetation dynamics. Coupled stomatal conductance and carbon assimilation (A - g{sub s}) models have been widely used as part of land surface parameterizations in climate models to describe the biogeophysical and biogeochemical roles of terrestrial vegetation. Differences in various A - g{sub s} schemes produce substantial differences in the estimation of carbon assimilation and canopy transpiration, as well as in other land-atmosphere fluxes. The terrestrial carbon assimilation and canopy transpiration simulated by two different representative A - g{sub s} schemes, a simple A-g{sub s} scheme adopted from the treatments of the NCAR model (Scheme I) and a two-big-leaf A - g{sub s} scheme newly developed by Dai et al. (J Clim 17:2281-2299, 2004) (Scheme II), are compared via some sensitivity experiments to investigate impacts of different A - g{sub s} schemes on the simulations. Major differences are found in the estimate of canopy carbon assimilation rate, canopy conductance and canopy transpiration between the two schemes, primarily due to differences in (a) functional forms used to estimate parameters for carbon assimilation sub-models, (b) co-limitation methods used to estimate carbon assimilation rate from the three limiting rates, and (c) leaf-to-canopy scaling schemes. On the whole, the differences in the scaling approach are the largest contributor to the simulation discrepancies, but the different methods of co-limitation of assimilation rate also impact the results. Except for a few biomes, the residual effects caused by the different parameter estimations in assimilation sub-models are relatively small. It is also noted that the two-leaf temperature scheme produces distinctly different sunlit and shaded leaf temperatures but has negligible impacts on the simulation of the carbon assimilation. (orig.)

  13. Variation in forest canopy nitrogen and albedo in response to N fertilization and elevated CO2

    Science.gov (United States)

    Wicklein, H. F.; Ollinger, S. V.; Martin, M.; Hollinger, D. Y.; Collatz, G. J.

    2009-12-01

    It is important to understand how high levels of nitrogen (N) deposition, through changes in N status, could influence a forest’s albedo and photosynthetic rates, and therefore the forest’s overall feedback (positive or negative) to global warming. Foliar N and albedo have recently been shown to covary at the canopy level across temperate and boreal forests. The purpose of this study is to examine the nature of this relationship from leaf to canopy scales and how it might change in response N and CO2 fertilization. Research was conducted at two long-term forest experimental sites. The chronic N amendment site at Harvard Forest in Petersham, MA includes three treatments: high N (fertilized with 150 kg N ha-1 yr-1), low N (50 kg N ha-1 yr-1), and ambient deposition (around 8 kg N ha-1 yr-1). The Oak Ridge National Environmental Research Park in Oak Ridge, TN includes a Free Air CO2 Enrichment (FACE) site where plots receive either ambient and elevated CO2 (540 ppm), and an N amendment site where plots are either fertilized with N (200 kg N ha-1 yr-1) or receive ambient deposition (10-15 kg N ha-1 yr-1). At Harvard Forest we measured seven black oak (Quercus velutina) and five red maple (Acer rubrum) trees in each treatment plot. At Oak Ridge we measured five sweetgum (Liquidambar styraciflua) trees in each FACE treatment plot, and four sweetgum trees in each N amendment treatment plot. Leaves were collected from two to three canopy heights from trees in each treatment plot. For each tree height we measured reflectance and transmittance spectra for stacks of 1, 2, 4, and 8 leaves, both abaxial and adaxial sides. We also measured N concentration, water content, and leaf mass per unit area (LMA) of the leaves. Canopy-level reflectance was modeled using the Scattering by Arbitrarily Inclined Leaves (SAIL-2) radiative transfer model. Preliminary results show significant differences in average leaf-level reflectance in the N fertilized treatments, with higher NIR

  14. Carbon-nitrogen interactions in forest ecosystems

    DEFF Research Database (Denmark)

    Gundersen, Per; Berg, Bjørn; Currie, W.S.;

    This report is a summary of the main results from the EU project “CarbonNitrogen Interactions in Forest Ecosystems” (CNTER). Since carbon (C) and nitrogen (N) are bound together in organic matter we studied both the effect of N deposition on C cycling in forest ecosystems, and the effect of C...

  15. BENTHIC METABOLISM ON A SHELTERED ROCKY SHORE: ROLE OF THE CANOPY IN THE CARBON BUDGET(1).

    Science.gov (United States)

    Golléty, Claire; Migné, Aline; Davoult, Dominique

    2008-10-01

    While the importance of canopy-forming algae in structuring ecosystems is recognized, their role in the carbon budget is still not well understood. To our knowledge, no measurements of rocky shores primary production and respiration under emersion periods have been carried out in situ. A benthic chamber coupled to a CO2 -infrared gas analyzer was used to measure gross primary production and respiration on the Ascophyllum nodosum (L.) Le Jol. zone of a sheltered rocky shore in Brittany, France. Over a year of monthly measurements on the zone with and without the A. nodosum canopy showed fairly high production and respiration values for the global community as well as carbon fluxes due to the canopy that largely dominated the benthic metabolism of the zone. The strong canopy respiration relative to the primary production also suggested a high metabolic activity by microscopic heterotrophs on the surface of the alga. Both the canopy and the understory annual primary production and respiration were under the control of light and temperature seasonal variations. Finally, the range of the amount of carbon produced on the A. nodosum zone during diurnal emersions was estimated. Additional measures accounting for the day-night cycles and seasonal light variations over an entire tidal cycle are, however, necessary to establish an annual carbon budget. Such measures using the benthic chamber together with complementary techniques would allow a better understanding of the functioning of sheltered rocky shores.

  16. Steady state estimation of soil organic carbon using satellite-derived canopy leaf area index

    Science.gov (United States)

    Fang, Yilin; Liu, Chongxuan; Huang, Maoyi; Li, Hongyi; Leung, L. Ruby

    2014-12-01

    Estimation of soil organic carbon (SOC) stock using models typically requires long term spin-up of the carbon-nitrogen (CN) models, which has become a bottleneck for global modeling. We report a new numerical approach to estimate global SOC stock that can alleviate long spin-up. The approach uses satellite-based canopy leaf area index (LAI) and takes advantage of a reaction-based biogeochemical module—Next Generation BioGeoChemical Module (NGBGC) that was recently developed and incorporated in version 4 of the Community Land Model (CLM4). Although NGBGC uses the same CN mechanisms as in CLM4CN, it can be easily configured to run prognostic or steady state simulations. The new approach was applied at point and global scales and compared with SOC derived from spin-up by running NGBGC in the prognostic mode, and SOC from the Harmonized World Soil Database (HWSD). The steady state solution is comparable to the spin-up value when the satellite LAI is close to that from the spin-up solution, and largely captured the global variability of the HWSD SOC across the different dominant plant functional types (PFTs). The correlation between the simulated and HWSD SOC was, however, weak at both point and global scales, suggesting the needs for improving the biogeochemical processes described in CLM4 and updating HWSD. Besides SOC, the steady state solution also includes all other state variables simulated by a spin-up run, which makes the tested approach a promising tool to efficiently estimate global SOC distribution and evaluate and compare multiple aspects simulated by different CN mechanisms in the model.

  17. Carbon-nitrogen interactions in forest ecosystems

    DEFF Research Database (Denmark)

    Gundersen, Per; Berg, Bjørn; Currie, W.S.;

    This report is a summary of the main results from the EU project “CarbonNitrogen Interactions in Forest Ecosystems” (CNTER). Since carbon (C) and nitrogen (N) are bound together in organic matter we studied both the effect of N deposition on C cycling in forest ecosystems, and the effect of C...... accumulation on N storage and release. Based on compiled databases on element pools and fluxes from several hundred forest sites, process studies in long-term nitrogen manipulation experiments and modelling efforts we estimated C sequestration and N retention in European forest soils. Further, we studied...... the impact of forest management on C sequestration, N retention and N leaching....

  18. Prediction of boron carbon nitrogen phase diagram

    Science.gov (United States)

    Yao, Sanxi; Zhang, Hantao; Widom, Michael

    We studied the phase diagram of boron, carbon and nitrogen, including the boron-carbon and boron-nitrogen binaries and the boron-carbon-nitrogen ternary. Based on the idea of electron counting and using a technique of mixing similar primitive cells, we constructed many ''electron precise'' structures. First principles calculation is performed on these structures, with either zero or high pressures. For the BN binary, our calculation confirms that a rhmobohedral phase can be stablized at high pressure, consistent with some experimental results. For the BCN ternary, a new ground state structure is discovered and an Ising-like phase transition is suggested. Moreover, we modeled BCN ternary phase diagram and show continuous solubility from boron carbide to the boron subnitride phase.

  19. Modelling the carbon and nitrogen cycles

    Directory of Open Access Journals (Sweden)

    Costas A Varotsos

    2014-04-01

    Full Text Available The issues of air pollution are inextricably linked to the mechanisms underlying the physicochemical functioning of the biosphere which together with the atmosphere, the cryosphere, the lithosphere, and the hydrosphere constitute the climate system. We herewith present a review of the achievements and unresolved problems concerning the modeling of the biochemical cycles of basic chemicals of the climate system, such as carbon and nitrogen. Although the achievements in this area can roughly describe the carbon and nitrogen cycles, serious problems still remain associated with the accuracy and precision of the processes and assessments employed in the relevant modeling.

  20. On The Cosmic Origins Of Carbon & Nitrogen

    CERN Document Server

    Henry, R B C; Köppen, J

    2001-01-01

    We employ analytical and numerical chemical evolution models to study observed trends in abundance ratios involving carbon, nitrogen, and oxygen. Several sets of published stellar yields for both intermediate-mass and massive stars are considered, and the most appropriate sets are selected through the use of analytical models. These yields are then used in the numerical models to match observed data trends in C/O, N/O, and O/H. We conclude that the principal production site for carbon is massive stars, while that for nitrogen is intermediate-mass stars.

  1. Worldwide organic soil carbon and nitrogen data

    Energy Technology Data Exchange (ETDEWEB)

    Zinke, P.J.; Stangenberger, A.G. [Univ. of California, Berkeley, CA (United States). Dept. of Forestry and Resource Management; Post, W.M.; Emanual, W.R.; Olson, J.S. [Oak Ridge National Lab., TN (United States)

    1986-09-01

    The objective of the research presented in this package was to identify data that could be used to estimate the size of the soil organic carbon pool under relatively undisturbed soil conditions. A subset of the data can be used to estimate amounts of soil carbon storage at equilibrium with natural soil-forming factors. The magnitude of soil properties so defined is a resulting nonequilibrium values for carbon storage. Variation in these values is due to differences in local and geographic soil-forming factors. Therefore, information is included on location, soil nitrogen content, climate, and vegetation along with carbon density and variation.

  2. Spatial Variability Analysis of Within-Field Winter Wheat Nitrogen and Grain Quality Using Canopy Fluorescence Sensor Measurements

    Directory of Open Access Journals (Sweden)

    Xiaoyu Song

    2017-03-01

    Full Text Available Wheat grain protein content (GPC is a key component when evaluating wheat nutrition. It is also important to determine wheat GPC before harvest for agricultural and food process enterprises in order to optimize the wheat grading process. Wheat GPC across a field is spatially variable due to the inherent variability of soil properties and position in the landscape. The objectives of this field study were: (i to assess the spatial and temporal variability of wheat nitrogen (N attributes related to the grain quality of winter wheat production through canopy fluorescence sensor measurements; and (ii to examine the influence of spatial variability of soil N and moisture across different growth stages on the wheat grain quality. A geostatistical approach was used to analyze data collected from 110 georeferenced locations. In particular, Ordinary Kriging Analysis (OKA was used to produce maps of wheat GPC, GPC yield, and wheat canopy fluorescence parameters, including simple florescence ratio and Nitrogen Balance Indices (NBI. Soil Nitrate-Nitrogen (NO3-N content and soil Time Domain Reflectometry (TDR value in the study field were also interpolated through the OKA method. The fluorescence parameter maps, soil NO3-N and soil TDR maps obtained from the OKA output were compared with the wheat GPC and GPC yield maps in order to assess their relationships. The results of this study indicate that the NBI spatial variability map in the late stage of wheat growth can be used to distinguish areas that produce higher GPC.

  3. Spectral measurements at different spatial scales in potato: relating leaf, plant and canopy nitrogen status

    NARCIS (Netherlands)

    Jongschaap, R.E.E.; Booij, R.

    2004-01-01

    Chlorophyll contents in vegetation depend on soil nitrogen availability and on crop nitrogen uptake, which are important management factors in arable farming. Crop nitrogen uptake is important, as nitrogen is needed for chlorophyll formation, which is important for photosynthesis, i.e. the conversio

  4. Interactions between leaf nitrogen status and longevity in relation to N cycling in three contrasting European forest canopies

    Directory of Open Access Journals (Sweden)

    L. Wang

    2013-02-01

    Full Text Available Seasonal and spatial variations in foliar nitrogen (N parameters were investigated in three European forests with different tree species, viz. beech (Fagus sylvatica L., Douglas fir (Pseudotsuga menziesii (Mirb. Franco and Scots pine (Pinus sylvestris L. growing in Denmark, the Netherlands and Finland, respectively. The objectives were to investigate the distribution of N pools within the canopies of the different forests and to relate this distribution to factors and plant strategies controlling leaf development throughout the seasonal course of a vegetation period. Leaf N pools generally showed much higher seasonal and vertical variability in beech than in the coniferous canopies. However, also the two coniferous tree species behaved very differently with respect to peak summer canopy N content and N re-translocation efficiency, showing that generalisations on tree internal vs. ecosystem internal N cycling cannot be made on the basis of the leaf duration alone. During phases of intensive N turnover in spring and autumn, the NH4+ concentration in beech leaves rose considerably, while fully developed green beech leaves had relatively low tissue NH4+, similar to the steadily low levels in Douglas fir and, particularly, in Scots pine. The ratio between bulk foliar concentrations of NH4+ and H+, which is an indicator of the NH3 emission potential, reflected differences in foliage N concentration, with beech having the highest values followed by Douglas fir and Scots pine. Irrespectively of the leaf habit, i.e. deciduous versus evergreen, the majority of the canopy foliage N was retained within the trees. This was accomplished through an effective N re-translocation (beech, higher foliage longevity (fir or both (boreal pine forest. In combination with data from a literature review, a general relationship of decreasing N re

  5. Interactions between leaf nitrogen status and longevity in relation to N cycling in three contrasting European forest canopies

    Science.gov (United States)

    Wang, L.; Ibrom, A.; Korhonen, J. F. J.; Arnoud Frumau, K. F.; Wu, J.; Pihlatie, M.; Schjoerring, J. K.

    2013-02-01

    Seasonal and spatial variations in foliar nitrogen (N) parameters were investigated in three European forests with different tree species, viz. beech (Fagus sylvatica L.), Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and Scots pine (Pinus sylvestris L.) growing in Denmark, the Netherlands and Finland, respectively. The objectives were to investigate the distribution of N pools within the canopies of the different forests and to relate this distribution to factors and plant strategies controlling leaf development throughout the seasonal course of a vegetation period. Leaf N pools generally showed much higher seasonal and vertical variability in beech than in the coniferous canopies. However, also the two coniferous tree species behaved very differently with respect to peak summer canopy N content and N re-translocation efficiency, showing that generalisations on tree internal vs. ecosystem internal N cycling cannot be made on the basis of the leaf duration alone. During phases of intensive N turnover in spring and autumn, the NH4+ concentration in beech leaves rose considerably, while fully developed green beech leaves had relatively low tissue NH4+, similar to the steadily low levels in Douglas fir and, particularly, in Scots pine. The ratio between bulk foliar concentrations of NH4+ and H+, which is an indicator of the NH3 emission potential, reflected differences in foliage N concentration, with beech having the highest values followed by Douglas fir and Scots pine. Irrespectively of the leaf habit, i.e. deciduous versus evergreen, the majority of the canopy foliage N was retained within the trees. This was accomplished through an effective N re-translocation (beech), higher foliage longevity (fir) or both (boreal pine forest). In combination with data from a literature review, a general relationship of decreasing N re-translocation efficiency with the time needed for canopy renewal was deduced, showing that leaves which live longer re

  6. Effects of nitrogen application rate and leaf age on the distribution pattern of leaf SPAD readings in the rice canopy.

    Directory of Open Access Journals (Sweden)

    Hu Yang

    Full Text Available A Soil-Plant Analysis Development (SPAD chlorophyll meter can be used as a simple tool for evaluating N concentration of the leaf and investigating the combined effects of nitrogen rate and leaf age on N distribution. We conducted experiments in a paddy field over two consecutive years (2008-2009 using rice plants treated with six different N application levels. N distribution pattern was determined by SPAD readings based on the temporal dynamics of N concentrations in individual leaves. At 62 days after transplantation (DAT in 2008 and DAT 60 in 2009, leaf SPAD readings increased from the upper to lower in the rice canopy that received N levels of 150 to 375 kg ha(-1The differences in SPAD readings between the upper and lower leaf were larger under higher N application rates. However, as plants grew, this atypical distribution of SPAD readings in canopy leaf quickly reversed to the general order. In addition, temporal dynamics of the leaf SPAD readings (N concentrations were fitted to a piecewise function. In our model, changes in leaf SPAD readings were divided into three stages: growth, functioning, and senescence periods. The leaf growth period lasted approximately 6 days, and cumulative growing days were not affected by N application rates. The leaf functioning period was represented with a relatively stable SPAD reading related to N application rate, and cumulative growing days were extended with increasing N application rates. A quadratic equation was utilized to describe the relationship between SPAD readings and leaf age during the leaf senescence period. The rate of decrease in SPAD readings increased with the age of leaves, but the rate was slowed by N application. As leaves in the lower canopy were physiologically older than leaves in the upper canopy, the rate of decrease in SPAD readings was faster in the lower leaves.

  7. Consistent effects of canopy vs. understory nitrogen addition on the soil exchangeable cations and microbial community in two contrasting forests.

    Science.gov (United States)

    Shi, Leilei; Zhang, Hongzhi; Liu, Tao; Zhang, Weixin; Shao, Yuanhu; Ha, Denglong; Li, Yuanqiu; Zhang, Chuangmao; Cai, Xi-an; Rao, Xingquan; Lin, Yongbiao; Zhou, Lixia; Zhao, Ping; Ye, Qing; Zou, Xiaoming; Fu, Shenglei

    2016-05-15

    Anthropogenic N deposition has been well documented to cause substantial impacts on the chemical and biological properties of forest soils. In most studies, however, atmospheric N deposition has been simulated by directly adding N to the forest floor. Such studies thus ignored the potentially significant effect of some key processes occurring in forest canopy (i.e., nitrogen retention) and may therefore have incorrectly assessed the effects of N deposition on soils. Here, we conducted an experiment that included both understory addition of N (UAN) and canopy addition of N (CAN) in two contrasting forests (temperate deciduous forest vs. subtropical evergreen forest). The goal was to determine whether the effects on soil exchangeable cations and microbial biomass differed between CAN and UAN. We found that N addition reduced pH, BS (base saturation) and exchangeable Ca and increased exchangeable Al significantly only at the temperate JGS site, and reduced the biomass of most soil microbial groups only at the subtropical SMT site. Except for soil exchangeable Mn, however, effects on soil chemical properties and soil microbial community did not significantly differ between CAN and UAN. Although biotic and abiotic soil characteristics differ significantly and the responses of both soil exchangeable cations and microbial biomass were different between the two study sites, we found no significant interactive effects between study site and N treatment approach on almost all soil properties involved in this study. In addition, N addition rate (25 vs. 50 kg N ha(-1) yr(-1)) did not show different effects on soil properties under both N addition approaches. These findings did not support previous prediction which expected that, by bypassing canopy effects (i.e., canopy retention and foliage fertilization), understory addition of N would overestimate the effects of N deposition on forest soil properties, at least for short time scale.

  8. Predicting Nitrogen Status of Rice Using Multispectral Data at Canopy Scale

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jin-Heng; WANG Ke; J. S. BAILEY; WANG Ren-Chao

    2006-01-01

    Two field experiments were conducted in Jiashan and Yuhang towns of Zhejiang Province, China, to study the feasibility of predicting N status of rice using canopy spectral reflectance. The canopy spectral reflectance of rice grown with different levels of N inputs was determined at several important growth stages. Statistical analyses showed that as a result of the different levels of N supply, there were significant differences in the N concentrations of canopy leaves at different growth stages. Since spectral reflectance measurements showed that the N status of rice was related to reflectance in the visible and NIR (near-infrared) ranges, observations for rice in 1 nm bandwidths were then converted to bandwidths in the visible and NIR spectral regions with IKONOS (space imaging) bandwidths and vegetation indices being used to predict the N status of rice. The results indicated that canopy reflectance measurements converted to ratio vegetation index (RVI) and normalized difference vegetation index (NDVI) for simulated IKONOS bands provided a better prediction of rice N status than the reflectance measurements in the simulated IKONOS bands themselves. The precision of the developed regression models using RVI and NDVI proved to be very high with R2 ranging from 0.82 to 0.94, and when validated with experimental data from a different site, the results were satisfactory with R2 ranging from 0.55 to 0.70.Thus, the results showed that theoretically it should be possible to monitor N status using remotely sensed data.

  9. A Model-Based Analysis of Nitrogen Deposition: Effects on Forest Carbon Sequestration

    Science.gov (United States)

    Dezi, S.; Medlyn, B. E.; Tonon, G.; Magnani, F.

    2009-04-01

    Over the last 150 years nitrogen deposition has increased, especially in the northern hemisphere, mainly due to the use of fossil fuels, deforestation and agricultural practices. Although the impact of this increase on the terrestrial carbon cycle is still uncertain, it is likely that this large perturbation of the global nitrogen cycle will have important effects on carbon cycling, particularly via impacts on forest carbon storage. In the present work we investigated qualitatively the overall response of forest carbon sequestration to nitrogen deposition, and the relative importance of different mechanisms that bring about this response. For this purpose we used the G'DAY forest carbon-nitrogen cycling model (Comins and McMurtrie 1993), introducing some new assumptions which focus on the effect of nitrogen deposition. Specifically the new assumptions are: (i) foliar litterfall and specific leaf area (SLA) are functions of leaf nitrogen concentration; (ii) belowground C allocation is a function of net primary production (NPP); (iii) forest canopies can directly take up nitrogen; (iv) management of forests occurs; (v) leaching occurs only for nitrate nitrogen. We investigated the effect of each assumption on net ecosystem production (NEP), with a step increase in nitrogen deposition from a steady state of 0.4 gN m-2 yr-1 to 2 gN m-2 yr-1, and then running the old and new model versions for different nitrogen deposition levels. Our analysis showed that nitrogen deposition can have a large effect on forest carbon storage at ecosystem level. In particular the effect of the assumptions (ii), (iii) and (iv) seem to be of greater importance, giving rise to a markedly higher level of forest carbon sequestration than in their absence. On the contrary assumptions (i) and (v) seem not to have any particular effect on the NEP simulated. Finally, running the models for different levels of nitrogen deposition showed that estimating forest carbon exchange without taking into

  10. Soil Carbon and Nitrogen Cycle Modeling

    Science.gov (United States)

    Woo, D.; Chaoka, S.; Kumar, P.; Quijano, J. C.

    2012-12-01

    Second generation bioenergy crops, such as miscanthus (Miscantus × giganteus) and switchgrass (Panicum virgatum), are regarded as clean energy sources, and are an attractive option to mitigate the human-induced climate change. However, the global climate change and the expansion of perennial grass bioenergy crops have the power to alter the biogeochemical cycles in soil, especially, soil carbon storages, over long time scales. In order to develop a predictive understanding, this study develops a coupled hydrological-soil nutrient model to simulate soil carbon responses under different climate scenarios such as: (i) current weather condition, (ii) decreased precipitation by -15%, and (iii) increased temperature up to +3C for four different crops, namely miscanthus, switchgrass, maize, and natural prairie. We use Precision Agricultural Landscape Modeling System (PALMS), version 5.4.0, to capture biophysical and hydrological components coupled with a multilayer carbon and ¬nitrogen cycle model. We apply the model at daily time scale to the Energy Biosciences Institute study site, located in the University of Illinois Research Farms, in Urbana, Illinois. The atmospheric forcing used to run the model was generated stochastically from parameters obtained using available data recorded in Bondville Ameriflux Site. The model simulations are validated with observations of drainage and nitrate and ammonium concentrations recorded in drain tiles during 2011. The results of this study show (1) total soil carbon storage of miscanthus accumulates most noticeably due to the significant amount of aboveground plant carbon, and a relatively high carbon to nitrogen ratio and lignin content, which reduce the litter decomposition rate. Also, (2) the decreased precipitation contributes to the enhancement of total soil carbon storage and soil nitrogen concentration because of the reduced microbial biomass pool. However, (3) an opposite effect on the cycle is introduced by the increased

  11. Forests, nitrogen and albedo, a very interesting trio indeed

    Directory of Open Access Journals (Sweden)

    Borghetti M

    2009-01-01

    Full Text Available A short comment is made on a recent paper (Ollinger et al. 2008 which shows that forest ecosystem carbon uptake in temperate and boreal forests is directly related to canopy nitrogen concentration and that both carbon uptake capacity and canopy nitrogen concentration are positively correlated with shortwave surface albedo measured with broad-band satellite sensors.

  12. Feasibility of Field Evaluation of Rice Nitrogen Status From Reflectance Spectra of Canopy

    Institute of Scientific and Technical Information of China (English)

    WANGRENCAHO; WANGKE; 等

    1998-01-01

    Techniques for measurement of the N status of rice can be an aid to making manaement decisions with economic and environmental implications.A field experiment was conuced to identify spectral variables most sensitive to N deficiency detection in rice canopy with the possibiliy for their use as a management tool. Spectral and agronomic measurements were collected in the evaluation experiment of N status from rice canopy under vive N treatments in a silt loam soil ,Nitroen fertilization effects were seen across the entire wavelength measured .Red refectance decreased and near infrared reflectance increased with increasing N fertilizer application.Spectral differences between treatments were seen throughout the test period.The naer infrared refectnce/red reflectance ration (RVI) differed mored between treatment than between single bands.Variations in canopy reflectances due to other environmental factors were reduced by the use of RVI.In the spectral variables examined ,the RVI separated the treatments most effectively,and three or four treatments can be separated.Differences in spetral responses betwenn the treatments were attributable to leaf area index ,leaf chlorophyll concentration and phtomass,wich all changed with N fertilization.

  13. Nitrogen restrictions buffer modeled interactions of water with the carbon cycle

    Science.gov (United States)

    Huang, Yuanyuan; Gerber, Stefan

    2016-01-01

    Terrestrial carbon and water cycles are coupled at multiple spatiotemporal scales and are crucial to carbon sequestration. Water related climate extremes, such as drought and intense precipitation, can substantially affect the carbon cycle. Meanwhile, nitrogen is a limiting resource to plant and has therefore the potential to alter the coupling of water and carbon cycles on land. Here we assess the effect of nitrogen limitation on the response of the terrestrial carbon cycle to moisture anomalies using Geophysical Fluid Dynamics Laboratory's land surface model LM3V-N. We analyzed the response of three central carbon fluxes: net primary productivity (NPP), heterotrophic respiration (Rh), and net ecosystem productivity (NEP, the difference between NPP and Rh) and how these fluxes were altered under anomalies of the standardized precipitation and evapotranspiration index (SPEI). We found that globally, the correlations between each of the carbon flux and SPEI depended on the timescale and a strong legacy effect of SPEI anomalies on Rh. Consideration of nitrogen constraints reduced anomalies in carbon fluxes in response to extreme dry/wet events. This nitrogen-induced buffer constrained the growth of plants under wet extremes and allowed for enhanced growth during droughts. Extra gain of soil moisture from the downregulation of canopy transpiration by nitrogen limitation and shifts in the relative importance of water and nitrogen limitation during dry/wet extreme events are possible mechanisms contributing to the buffering of modeled NPP and NEP. Responses of Rh to moisture anomalies were much weaker compared to NPP, and N buffering effects were less evident.

  14. Effect of shoot removal on remobilization of carbon and nitrogen during regrowth of nitrogen-fixing alfalfa.

    Science.gov (United States)

    Aranjuelo, Iker; Molero, Gemma; Erice, Gorka; Aldasoro, Joseba; Arrese-Igor, Cesar; Nogués, Salvador

    2015-01-01

    The contribution of carbon and nitrogen reserves to regrowth following shoot removal has been studied in the past. However, important gaps remain in understanding the effect of shoot cutting on nodule performance and its relevance during regrowth. In this study, isotopic labelling was conducted at root and canopy levels with both (15) N2 and (13) C-depleted CO2 on exclusively nitrogen-fixing alfalfa plants. As expected, our results indicate that the roots were the main sink organs before shoots were removed. Seven days after regrowth the carbon and nitrogen stored in the roots was invested in shoot biomass formation and partitioned to the nodules. The large depletion in nodule carbohydrate availability suggests that root-derived carbon compounds were delivered towards nodules in order to sustain respiratory activity. In addition to the limited carbohydrate availability, the upregulation of nodule peroxidases showed that oxidative stress was also involved during poor nodule performance. Fourteen days after cutting, and as a consequence of the stimulated photosynthetic and N2 -fixing machinery, availability of Cnew and Nnew strongly diminished in the plants due to their replacement by C and N assimilated during the post-labelling period. In summary, our study indicated that during the first week of regrowth, root-derived C and N remobilization did not overcome C- and N-limitation in nodules and leaves. However, 14 days after cutting, leaf and nodule performance were re-established.

  15. Nitrogen and Carbon Dynamics Across Trophic Levels Along an Atmospheric Nitrogen Deposition Gradient

    Science.gov (United States)

    Wissinger, B. D.; Bell, M. D.; Newingham, B. A.

    2011-12-01

    Atmospheric nitrogen deposition has altered soil biogeochemical processes and plant communities across the United States. Prior investigations have demonstrated these alterations; however, little is known about the effects of elevated nitrogen on higher trophic levels. Building upon previous research that revealed an atmospheric nitrogen deposition gradient from the San Bernardino Mountains through Joshua Tree National Park in California, we investigated atmospheric nitrogen and its effects on soils, plants, and harvester ants. We measured nitrogen and carbon concentrations, along with carbon and nitrogen stable isotopes, across trophic levels at eighteen urban and unpopulated sites along the deposition gradient. Carbon and nitrogen attributes were determined in atmospheric nitric acid, soil, Larrea tridentata and Ambrosia dumosa leaves, seeds from selected plant species, and ants. We predicted carbon and nitrogen ratios and isotopes to change in areas with higher nitrogen deposition and vary along the deposition gradient. Nitrogen (p=0.02) and carbon (p=0.05) concentrations, as well as C:N ratios (p=<0.001), significantly differed in Messor pergandei individuals among sites; however, no correlation was found between these carbon and nitrogen attributes and the nitrogen deposition gradient (%N r2=0.02, %C r2=0.007, C:N r2=0.02). The δ15N and δ13C values of the ants, leaf tissues, and seeds measured across the gradient follow similar patterns with r2 values all below 0.20. Our results suggest the current and previous rates of nitrogen deposition in this area are not enough to modify nitrogen and carbon concentrations and isotope values. Compensatory nitrogen cycling processes in the soil may reduce the effects of increased nitrogen on plants and thus higher trophic levels. Nitrogen and carbon dynamics across trophic levels might change after longer ecosystem exposure to elevated nitrogen; however, other abiotic and biotic factors are likely driving current

  16. Discriminating tropical grass (Cenchrus ciliaris) canopies grown under different nitrogen treatment using spectroradiometry

    NARCIS (Netherlands)

    Mutanga, O.; Skidmore, A.K.; Wieren, van S.E.

    2003-01-01

    Techniques for estimating and mapping pasture quality are critical for a better understanding of wildlife and livestock grazing patterns. Nitrogen is one of the most important elements that determine quality in plants. We assessed the potential to discriminate differences in nitrogen concentration u

  17. Study on Nitrogen Distribution in Leaf, Stem and Sheath at Different Layers in Winter Wheat Canopy and Their Influence on Grain Quality

    Institute of Scientific and Technical Information of China (English)

    WANG Zhi-jie; WANG Ji-hua; HUANG Wen-jiang; MA Zhi-hong; ZHAO Ming

    2003-01-01

    Vertical distribution of nitrogen in wheat canopy, nitrogen remobilization and their influence on grain quality of winter wheat were studied. Two winter wheat cultivars, Jingdong8, a common cultivar, and Zhongyou9507, a high quality cultivar, were selected. Leaf nitrogen showed an obvious decreasing trend from the canopy top to the ground surface for all treatments in growth duration. There was no apparent vertical nitrogen gradient in stem and sheath of Zhongyou9507 compared with Jingdong8. Zhongyou9507 had more nitrogen remobilization from leaf, stem and sheath than Jingdong8 from middle grain filling to waxening, especially the nitrogen remobilization amount in stem and sheath, which was higher than that in Jingdong8 during growth duration. Higher vertical nitrogen gradients in Jingdong8 at anthesis had disadvantages on its grain quality. But higher vertical nitrogen gradients between middle and lower layers of Jingdong8 at grain filling stage enhanced its grain quality. Higher vertical nitrogen gradients in upper layer at anthesis and upper layer leaf and middle layer stem and sheath at grain filling stage had advantages on protein accumulation in grain of Zhongyou9507. There were positive correlations between foliar nitrogen remobilization amount and grain quality at later growth stage for the two cultivars. There was a positive correlation between quality of Jingdong8 and stem and sheath nitrogen remobilization amount from anthesis to early grain filling, and that of Zhongyou9507 emerged from anthesis to early grain filling and from middle grain filling to waxening. Contribution of leaf nitrogen to the quality of Jingdong8 was larger than nitrogen from stem and sheath. High protein content of Zhongyou9507 was attributed to the nitrogen condition in its leaf, stem and sheath. Nitrogen in stem and sheath played a more important role on the grain quality of Zhongyou9507 than on that of Jingdong8.

  18. Soil carbon and nitrogen dynamics linked to Piliostigma species in ferugino-tropical soils in the Sudano-Sahelian zone of Burkina Faso,West Africa

    Institute of Scientific and Technical Information of China (English)

    Barthélémy Yélémou; Sidzabda Djibril Dayamba; Dasmane Bambara; Georges Yaméogo; Salawu Assimi

    2013-01-01

    In the Sudano-Sahelian zone of Burkina Faso,Piliostigma reticulatum (DC) Hochst and Piliostigma thonningii (Schumach) are precursor species of fallow land colonization and they are used by rural villagers.The present study aimed to assess the contribution of Piliostigma species to soil quality improvement.We quantified organic carbon,total nitrogen,soil microbial biomass,soil basal respiration and metabolic quotient from soil samples taken under and outside Piliostigma canopies.We used one-way ANOVA to test for differences in the above parameters between locations (beneath and outside Piliostigma canopies).We recorded increased total organic carbon under Piliostigma from 31%-105% and in total nitrogen from 23%-66%.Microbial biomass was 13%-266% higher beneath canopies as compared to outside canopies.Basal respiration was also higher beneath canopies.The chemical elements varied by class of soil texture.Metabolic quotient (qCO2) was significantly correlated to clay (r =0.80) and silt (r =0.79) content.Piliostigma stands produced abundant litter due to their leaf biomass.Thus,they contribute to improved total organic carbon and total nitrogen content in the different phytogeographic zones and improve soil fertility

  19. Multicolor Nitrogen-Doped Carbon Dots for Live Cell Imaging.

    Science.gov (United States)

    Du, Fengyi; Li, Jianan; Hua, Ye; Zhang, Miaomiao; Zhou, Zhou; Yuan, Jing; Wang, Jun; Peng, Wanxin; Zhang, Li; Xia, Sheng; Wang, Dongqing; Yang, Shiming; Xu, Wenrong; Gong, Aihua; Shao, Qixiang

    2015-05-01

    Doping carbon dots with nitrogen atoms considerably enhances their fluorescence properties. However, the mechanism by which the carbon dots are doped is not fully understood. We developed a facile bottom-up hydrothermal carbonization (HTC) process that uses glucose and glycine as precursors for the synthesis of photoluminescent nitrogen-doped carbon dots. The as-prepared nitrogen-doped carbon dots were mono-dispersed spherical particles with a diameter of -2.8 nm. The doped nitrogen atoms assumed pyridinic type and pyrrolic type configurations to participate in the nanocrystal structure of the carbon dots. It appeared that the nitrogen doping introduces a new internal structure. The aqueous solution of nitrogen-doped carbon dots showed excitation wavelength-dependent multicolor photoluminescence. Further, these nitrogen-doped carbon dots readily entered the cytoplasm of A549 cancer cells and showed no significant cytotoxicity. The internalized nitrogen-doped carbon dots were localized to the cell membrane and cytoplasm, particularly around the nucleus. Further, the as-prepared, biocompatible, nitrogen-doped carbon dots demonstrated the potential to be used as fluorescent probes for multicolor live cell labeling, tracking, and imaging.

  20. Adaptation to high CO2 concentration in an optimal environment: radiation capture, canopy quantum yield and carbon use efficiency

    Science.gov (United States)

    Monje, O.; Bugbee, B.

    1998-01-01

    The effect of elevated [CO2] on wheat (Triticum aestivum L. Veery 10) productivity was examined by analysing radiation capture, canopy quantum yield, canopy carbon use efficiency, harvest index and daily C gain. Canopies were grown at either 330 or 1200 micromoles mol-1 [CO2] in controlled environments, where root and shoot C fluxes were monitored continuously from emergence to harvest. A rapidly circulating hydroponic solution supplied nutrients, water and root zone oxygen. At harvest, dry mass predicted from gas exchange data was 102.8 +/- 4.7% of the observed dry mass in six trials. Neither radiation capture efficiency nor carbon use efficiency were affected by elevated [CO2], but yield increased by 13% due to a sustained increase in canopy quantum yield. CO2 enrichment increased root mass, tiller number and seed mass. Harvest index and chlorophyll concentration were unchanged, but CO2 enrichment increased average life cycle net photosynthesis (13%, P < 0.05) and root respiration (24%, P < 0.05). These data indicate that plant communities adapt to CO2 enrichment through changes in C allocation. Elevated [CO2] increases sink strength in optimal environments, resulting in sustained increases in photosynthetic capacity, canopy quantum yield and daily C gain throughout the life cycle.

  1. Adaptation to high CO2 concentration in an optimal environment: radiation capture, canopy quantum yield and carbon use efficiency

    Science.gov (United States)

    Monje, O.; Bugbee, B.

    1998-01-01

    The effect of elevated [CO2] on wheat (Triticum aestivum L. Veery 10) productivity was examined by analysing radiation capture, canopy quantum yield, canopy carbon use efficiency, harvest index and daily C gain. Canopies were grown at either 330 or 1200 micromoles mol-1 [CO2] in controlled environments, where root and shoot C fluxes were monitored continuously from emergence to harvest. A rapidly circulating hydroponic solution supplied nutrients, water and root zone oxygen. At harvest, dry mass predicted from gas exchange data was 102.8 +/- 4.7% of the observed dry mass in six trials. Neither radiation capture efficiency nor carbon use efficiency were affected by elevated [CO2], but yield increased by 13% due to a sustained increase in canopy quantum yield. CO2 enrichment increased root mass, tiller number and seed mass. Harvest index and chlorophyll concentration were unchanged, but CO2 enrichment increased average life cycle net photosynthesis (13%, P CO2 enrichment through changes in C allocation. Elevated [CO2] increases sink strength in optimal environments, resulting in sustained increases in photosynthetic capacity, canopy quantum yield and daily C gain throughout the life cycle.

  2. Evaluating a Coupled Carbon and Nitrogen Cycle Model at a Pacific Northwest Douglas-fir Forest in Canada

    Science.gov (United States)

    Arain, M.; Yuan, F.; Shaikh, M.; Black, T.

    2004-05-01

    Nitrogen availability could be a key factor to enhance or limit plant photosynthesis under global climate change. This study presents a coupled nitrogen and carbon cycle model incorporated in the Canadian Land Surface Scheme (CLASS) which is used in the Canadian General Circulation Model. The nitrogen cycle model, which follows Dickinson et al., 2002 is coupled to a previously derived carbon model in CLASS. Nitrogen cycling processes taken into account include biological fixation, soil mineralization, immobilization, nitrification, denitrification, volatilization, leaching, root uptake and allocation to various plant components. Root nitrogen uptake depends on soil mineral nitrogen content, ion physical transport, root interface, and also on plant-growth demand for this nutrient. Leaf Rubisco-nitrogen concentration was modeled to determine variations in maximum rate of Rubisco activity,Vcmax. The coupled carbon and nitrogen model was tested at a Douglas-fir forest, growing on Vancouver Island, British Columbia, Canada, using observed eddy covariance flux data from 1998 to 2000. Simulated carbon and nitrogen uptake/loss rates were in broad agreement with observation. The simulated annual soil mineralized nitrogen was 6.3, 5.3, and 6.0 g m-2 in 1998, 1999 and 2000, respectively. The annual nitrogen uptake was 1.78, 1.65, and 1.76 g m-2, respectively. The simulated leaf nitrogen ranged from 1.81 to 1.87 g m-2 leaf area in the growing season, while observed leaf nitrogen values were 1.7 g m-2 in the lower canopy, and 2.56 g m-2 in the upper canopy. Observed Rubisco nitrogen was about 17% of total leaf nitrogen as compared to 16% simulated value. The modeled Vcmax in top leaves (Vcmax0) was as low as 15 imol C m-2 s-1 during the non-growing season, and as high as 80 imol C m-2 s-1 during the full growing season. Comparison of half-hourly observed and simulated gross ecosystem productivity (GEP), ecosystem respiration (R) and net ecosystem productivity (NEP) from 1998

  3. Remote Sensing of Vegetation Nitrogen Content for Spatially Explicit Carbon and Water Cycle Estimation

    Science.gov (United States)

    Zhang, Y. L.; Miller, J. R.; Chen, J. M.

    2009-05-01

    Foliage nitrogen concentration is a determinant of photosynthetic capacity of leaves, thereby an important input to ecological models for estimating terrestrial carbon and water budgets. Recently, spectrally continuous airborne hyperspectral remote sensing imagery has proven to be useful for retrieving an important related parameter, total chlorophyll content at both leaf and canopy scales. Thus remote sensing of vegetation biochemical parameters has promising potential for improving the prediction of global carbon and water balance patterns. In this research, we explored the feasibility of estimating leaf nitrogen content using hyperspectral remote sensing data for spatially explicit estimation of carbon and water budgets. Multi-year measurements of leaf biochemical contents of seven major boreal forest species were carried out in northeastern Ontario, Canada. The variation of leaf chlorophyll and nitrogen content in response to various growth conditions, and the relationship between them,were investigated. Despite differences in plant type (deciduous and evergreen), leaf age, stand growth conditions and developmental stages, leaf nitrogen content was strongly correlated with leaf chlorophyll content on a mass basis during the active growing season (r2=0.78). With this general correlation, leaf nitrogen content was estimated from leaf chlorophyll content at an accuracy of RMSE=2.2 mg/g, equivalent to 20.5% of the average measured leaf nitrogen content. Based on this correlation and a hyperspectral remote sensing algorithm for leaf chlorophyll content retrieval, the spatial variation of leaf nitrogen content was inferred from the airborne hyperspectral remote sensing imagery acquired by Compact Airborne Spectrographic Imager (CASI). A process-based ecological model Boreal Ecosystem Productivity Simulator (BEPS) was used for estimating terrestrial carbon and water budgets. In contrast to the scenario with leaf nitrogen content assigned as a constant value without

  4. Leaf nitrogen distribution in relation to crown architecture in the tall canopy species, Fagus crenata.

    Science.gov (United States)

    Osada, Noriyuki; Yasumura, Yuko; Ishida, Atsushi

    2014-08-01

    The theory of optimal leaf N distribution predicts that the C gain of plants is maximized when the N content per unit area (N(area)) scales with light availability, but most previous studies have demonstrated that the N distribution is not proportional to light availability. In tall trees, the leaves are often clustered on twigs (leaf cluster) and not evenly distributed within the crowns. Thus, we hypothesized that the suboptimal N distribution is partly caused by the limited capacity to translocate N between leaf clusters, and consequently, the relationship between light and N(area) differs for leaves in different clusters. We investigated the light availability and N content of all individual leaves within several leaf clusters on tall trees of a deciduous canopy species Fagus crenata in Japan. We observed that the within-cluster leaf N distribution patterns differed from the between-cluster patterns and the slopes of the relationships between light and N(area) were lower within clusters than between clusters. According to the detailed analysis of the N distribution within leaf clusters, N(area) was greater for current-year shoots with greater light availability or a larger total leaf area. The latter pattern was probably caused by the greater sink strength of the current-year shoots with a larger leaf area. These N distribution patterns suggest that leaf clusters are fairly independent with respect to their N use, and the productivity of real F. crenata crowns may be less than optimal.

  5. Carbon-nitrogen interactions in forest ecosystems; final report

    NARCIS (Netherlands)

    Gundersen, P.; Berg, B.; Currie, W.S.; Dise, N.B.; Emmett, B.A.; Gauci, V.; Holmberg, M.; Kjønaas, O.J.; Mol-Dijkstra, J.P.; Salm, van der C.; Schmidt, I.K.; Tietema, A.; Wessel, W.W.; Vestgarden, L.S.; Akselsson, C.; Vries, de W.; Forsius, M.; Kros, H.; Matzner, E.; Moldan, F.; Nadelhoffer, K.J.; Nilsson, L.O.; Reinds, G.J.; Rosengren, U.; Stuanes, A.O.; Wright, R.F.

    2006-01-01

    This report is a summary of the main results from the EU project 'Carbon' - Nitrogen Interactions in Forest Ecosystems' (CNTER). Since carbon (C) and nitrogen (N) are bound together in organic matter we studied both the effect of N deposition on C cycling in forest ecosystems, and the effect of C ac

  6. Variation in Foliar Nitrogen and Albedo in Response to Elevated Nitrogen and Carbon Dioxide

    Science.gov (United States)

    Wicklein, H. F.; Ollinger, S. V.; Martin, M. M.; Hollinger, D. Y.; Bartlett, M. K.; Richardson, A. D.

    2010-12-01

    It has recently been demonstrated that foliar nitrogen (N) is positively correlated with midsummer canopy albedo over a broad range of plant functional types. However, the mechanism(s) driving the N- albedo relationship remain elusive, and it is unknown whether factors affecting N availability will also influence albedo. To address these questions, we investigated leaf spectral properties from three deciduous broadleaf species subjected to either N (Harvard Forest, MA and Oak Ridge, TN) or CO2 fertilization (Oak Ridge, TN), and compared results to measured chemical and structural properties. We measured reflectance and transmittance along with foliar N, leaf mass per unit area, and water content for stacks of 1, 2, 4, and 8 leaves. For the Oak Ridge, TN site, we also obtained canopy reflectance data from the airborne visible / infrared imaging spectrometer (AVIRIS) to examine whether canopy level spectral responses were consistent with leaf-level results. At the leaf level, results showed no significant differences in reflectance or transmittance between CO2 or N treatments, despite changes in N concentration caused by N fertilization. Although foliar N was significantly correlated with leaf shortwave and near infrared reflectance across species, the slope of both relationships was negative, which ran counter to our expectations. These results do not support the hypothesis that the canopy-level pattern is driven by leaf-level relationships. In contrast to leaf-level observations, remote sensing data from Oak Ridge did indicate an increase in NIR reflectance with N fertilization. Collectively, these results suggest that altered N availability may have an effect on canopy albedo, albeit by mechanisms that involve stem or canopy level processes rather than changes in leaf structure.

  7. Intercropping enhances soil carbon and nitrogen.

    Science.gov (United States)

    Cong, Wen-Feng; Hoffland, Ellis; Li, Long; Six, Johan; Sun, Jian-Hao; Bao, Xing-Guo; Zhang, Fu-Suo; Van Der Werf, Wopke

    2015-04-01

    Intercropping, the simultaneous cultivation of multiple crop species in a single field, increases aboveground productivity due to species complementarity. We hypothesized that intercrops may have greater belowground productivity than sole crops, and sequester more soil carbon over time due to greater input of root litter. Here, we demonstrate a divergence in soil organic carbon (C) and nitrogen (N) content over 7 years in a field experiment that compared rotational strip intercrop systems and ordinary crop rotations. Soil organic C content in the top 20 cm was 4% ± 1% greater in intercrops than in sole crops, indicating a difference in C sequestration rate between intercrop and sole crop systems of 184 ± 86 kg C ha(-1) yr(-1). Soil organic N content in the top 20 cm was 11% ± 1% greater in intercrops than in sole crops, indicating a difference in N sequestration rate between intercrop and sole crop systems of 45 ± 10 kg N ha(-1) yr(-1). Total root biomass in intercrops was on average 23% greater than the average root biomass in sole crops, providing a possible mechanism for the observed divergence in soil C sequestration between sole crop and intercrop systems. A lowering of the soil δ(15) N signature suggested that increased biological N fixation and/or reduced gaseous N losses contributed to the increases in soil N in intercrop rotations with faba bean. Increases in soil N in wheat/maize intercrop pointed to contributions from a broader suite of mechanisms for N retention, e.g., complementary N uptake strategies of the intercropped plant species. Our results indicate that soil C sequestration potential of strip intercropping is similar in magnitude to that of currently recommended management practises to conserve organic matter in soil. Intercropping can contribute to multiple agroecosystem services by increased yield, better soil quality and soil C sequestration.

  8. The response of gross nitrogen mineralization to labile carbon inputs

    Science.gov (United States)

    Bengtson, Per

    2014-05-01

    Input of labile carbon sources to forest soils commonly result in priming, i.e. an increase in the microbial decomposition of soil organic matter. Efforts aimed at quantifying the extent of priming have, to date, largely focused on soil organic matter decomposition manifested as soil respiration. Less is known about how gross nitrogen mineralization responds to input of labile carbon. It is often assumed that increased priming results in decreased soil carbon stocks. However, microbial mineralization of organic nitrogen into plant available forms is a major factor limiting primary production in forests. If increased decomposition of soil organic matter in response to labile carbon is accompanied by a concurrent increased nitrogen mineralization, this could result in elevated primary production and higher rates of plant derived organic matter input to soils. Therefore, in order to fully understand the effect of priming on net ecosystem exchange and soil carbon stocks, it is vital to consider if increased decomposition of soil organic matter caused by priming also results in increased nitrogen mineralization. Here I present the results from a series of experiments aimed at determining if, and to which extent, gross nitrogen mineralization is stimulated by input of labile carbon. The results suggest that it is by no means uncommon to find an increase in gross N mineralization rates in response to labile carbon inputs. The magnitude of the increase seems dependent on the nitrogen status of the soil, as well as the concentration and rate of labile carbon inputs. However, continuous input of labile carbon sources that also contains nitrogen, e.g. amino acids, seems to inhibit rather than increase the mineralization of organic nitrogen. These findings suggest that there is a potential for a positive feedback between priming and primary production that needs to be considered in order to fully understand the influence of priming on net ecosystem exchange and soil carbon

  9. Carbon and nitrogen balances for six shrublands across Europe

    DEFF Research Database (Denmark)

    Beier, Claus; Emmett, Bridget A.; Tietema, Albert

    2009-01-01

    and nitrogen balances of six shrublands along a climatic gradient across the European continent. The aim of the study was to provide a basis for assessing the range and variability in carbon storage in European shrublands. Across the sites the net carbon storage in the systems ranged from 1,163 g C m−2 to 18...... with a cold and wet climate where soil C constitutes 95% of the total carbon in the ecosystem. Respiration of carbon from the soil organic matter pool dominated the carbon loss at all sites while carbon loss from aboveground litter decomposition appeared less important. Total belowground carbon allocation...

  10. Optimization of Carbon Nanotubes for Nitrogen Gas Adsorption

    Directory of Open Access Journals (Sweden)

    Fereydoun Ashrafi

    2010-09-01

    Full Text Available Carbon nano-tubes are one of the most significant achievements of nano-technology with important applications in the design of electronic nano-devices. The study of their properties is therefore important. Here the density functional theory (DFT of electron and the Hartree-Fock (HF method are utilized to study the adsorption of nitrogen molecules on the surface of (4, 4 and (5, 0 carbon nano-tubes. The electronic structure, single point and dipole moment of both nitrogen and carbon nuclei are thoroughly studied. The computational results, which includes, indicate that rich adsorption patterns may result from the interaction of nitrogen with the carbon nano tubes sometimes C-N bounds are formed via breaking C-C bounds and sometimes a carbon atom in the nano-tube is replaced with a nitrogen atom. Sometimes nitrogen atoms are attracted to a C-C bound. In summary, the optimized adsorption rates are calculated. Gaussian 98 software has been used to carry out quantum chemistry calculations. Keywords: Density functional theory, Hartree-Fock, carbon nano tube, Gaussian 98 software. Carbon nanotubes (CNTs are one of the most significant achievements of nano-technology because of his important applications in the design of electronic nano-devices. The study of their properties is therefore important. In this investigation the Density Functional Theory (DFT of electron and the Hartree-Fock (HF method are utilized to study the adsorption of nitrogen molecules on the surface of (4, 4 and (5, 0 carbon nanotubes. The electronic structure, single point and dipole moment of both nitrogen and carbon nuclei are thoroughly studied. The computational results, which includes, indicate that rich adsorption patterns m ay result from the interaction of nitrogen with the carbon nanotubes. Sometimes C-N bounds are formed via breaking C-C bounds and sometimes a carbon atom in the nanotube is replaced by a nitrogen atom. Sometimes nitrogen atoms are attracted to a C-C bound

  11. Combining sap flow meas- urement-based canopy stomatal conductance and 13C discrimination to estimate forest carbon assimilation

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ping; LU Ping; MA Ling; SUN Guchou; RAO Xingquan; CAI Xian; ZENG Xiaoping

    2005-01-01

    The available methods for studying C uptake of forest and their problems in practices are reviewed, and a new approach to combining sap flow and 13C techniques is proposed in this paper. This approach, obtained through strict mathematic derivation, combines sap flow measurement-based canopy stomatal conductance and 13C discrimination to estimate instantaneous carbon assimilation rate of a forest. Namely the mean canopy stomatal conductance (gc) acquired from accurate measurement of sap flux density is integrated with the relationship between 13C discrimination (() and Ci/Ca (intercellular/ambient CO2 concentrations) and with that between Anet (net photosynthetic rate) and gCO2 (stomatal conductance for CO2) so that a new relation between forest C uptake and ( as well as gc is established. It is a new method of such kind for studying the C exchange between forest and atmosphere based on experimental ecology.

  12. Estimating foliar biochemistry from hyperspectral data in mixed forest canopy

    DEFF Research Database (Denmark)

    Huber Gharib, Silvia; Kneubühler, Mathias; Psomas, Achilleas

    2008-01-01

    data to estimate the foliar concentration of nitrogen, carbon and water in three mixed forest canopies in Switzerland. With multiple linear regression models, continuum-removed and normalized HyMap spectra were related to foliar biochemistry on an individual tree level. The six spectral wavebands used...

  13. Growth and metabolism of Saccharomyces cerevisiae in chemostat cultures under carbon-, nitrogen-, or carbon- and nitrogen-limiting conditions.

    OpenAIRE

    Larsson, C; von Stockar, U.; Marison, I; Gustafsson, L.

    1993-01-01

    Aerobic chemostat cultures of Saccharomyces cerevisiae were performed under carbon-, nitrogen-, and dual carbon- and nitrogen-limiting conditions. The glucose concentration was kept constant, whereas the ammonium concentration was varied among different experiments and different dilution rates. It was found that both glucose and ammonium were consumed at the maximal possible rate, i.e., the feed rate, over a range of medium C/N ratios and dilution rates. To a small extent, this was due to a c...

  14. Spectroscopic investigation of nitrogen-functionalized carbon materials

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Kevin N. [Department of Metallurgical and Materials Engineering, Colorado School of Mines, 1500 Illinois Street Golden CO 80401 USA; Department of Mechanical Engineering, University of Michigan, Ann Arbor MI 48109 USA; Christensen, Steven T. [National Renewable Energy Laboratory, 15013 Denver West Pkwy Golden CO 80401 USA; Nordlund, Dennis [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd Menlo Park CA 94023 USA; Dameron, Arrelaine A. [National Renewable Energy Laboratory, 15013 Denver West Pkwy Golden CO 80401 USA; Ngo, Chilan [Department of Chemistry and Geochemistry, Colorado School of Mines, 1012 14th Street Golden CO 80401 USA; Dinh, Huyen [National Renewable Energy Laboratory, 15013 Denver West Pkwy Golden CO 80401 USA; Gennett, Thomas [National Renewable Energy Laboratory, 15013 Denver West Pkwy Golden CO 80401 USA; O' Hayre, Ryan [Department of Metallurgical and Materials Engineering, Colorado School of Mines, 1500 Illinois Street Golden CO 80401 USA; Pylypenko, Svitlana [Department of Chemistry and Geochemistry, Colorado School of Mines, 1012 14th Street Golden CO 80401 USA

    2016-04-07

    Carbon materials are used in a diverse set of applications ranging from pharmaceuticals to catalysis. Nitrogen modification of carbon powders has shown to be an effective method for enhancing both surface and bulk properties of as-received material for a number of applications. Unfortunately, control of the nitrogen modification process is challenging and can limit the effectiveness and reproducibility of N-doped materials. Additionally, the assignment of functional groups to specific moieties on the surface of nitrogen-modified carbon materials is not straightforward. Herein, we complete an in-depth analysis of functional groups present at the surface of ion-implanted Vulcan and Graphitic Vulcan through the use of X-ray photoelectron spectroscopy (XPS) and near edge X-ray adsorption fine structure spectroscopy (NEXAFS). Our results show that regardless of the initial starting materials used, nitrogen ion implantation conditions can be tuned to increase the amount of nitrogen incorporation and to obtain both similar and reproducible final distributions of nitrogen functional groups. The development of a well-controlled/reproducible nitrogen implantation pathway opens the door for carbon supported catalyst architectures to have improved numbers of nucleation sites, decreased particle size, and enhanced catalyst-support interactions.

  15. Carbon and nitrogen isotope variations in tree-rings as records of perturbations in regional carbon and nitrogen cycles.

    Science.gov (United States)

    Bukata, Andrew R; Kyser, T Kurtis

    2007-02-15

    Increasing anthropogenic pollution from urban centers and fossil fuel combustion can impact the carbon and nitrogen cycles in forests. To assess the impact of twentieth century anthropogenic pollution on forested system carbon and nitrogen cycles, variations in the carbon and nitrogen isotopic compositions of tree-rings were measured. Individual annual growth rings in trees from six sites across Ontario and one in New Brunswick, Canada were used to develop site chronologies of tree-ring delta 15N and delta 13C values. Tree-ring 615N values were approximately 0.5% per hundred higher and correlated with contemporaneous foliar samples from the same tree, but not with delta 15N values of soil samples. Temporal trends in carbon and nitrogen isotopic compositions of these tree-rings are consistent with increasing anthropogenic influence on both the carbon and nitrogen cycles since 1945. Tree-ring delta 13C values and delta 15N values are correlated at both remote and urban-proximal sites, with delta 15N values decreasing since 1945 and converging on 1% per hundred at urban-proximal sites and decreasing but not converging on a single delta 15N value in remote sites. These results indicate that temporal trends in tree-ring nitrogen and carbon isotopic compositions record the regional extent of pollution.

  16. Temporal trends and sources of variation in carbon flux from coarse woody debris in experimental forest canopy openings.

    Science.gov (United States)

    Forrester, J A; Mladenoff, D J; D'Amato, A W; Fraver, S; Lindner, D L; Brazee, N J; Clayton, M K; Gower, S T

    2015-11-01

    Pulses of respiration from coarse woody debris (CWD) have been observed immediately following canopy disturbances, but it is unclear how long these pulses are sustained. Several factors are known to influence carbon flux rates from CWD, but few studies have evaluated more than temperature and moisture. We experimentally manipulated forest structure in a second-growth northern hardwood forest and measured CO2 flux periodically for seven growing seasons following gap creation. We present an analysis of which factors, including the composition of the wood-decay fungal community influence CO2 flux. CO2 flux from CWD was strongly and positively related to wood temperature and varied significantly between substrate types (logs vs. stumps). For five growing seasons after treatment, the CO2 flux of stumps reached rates up to seven times higher than that of logs. CO2 flux of logs did not differ significantly between canopy-gap and closed-canopy conditions in the fourth through seventh post-treatment growing seasons. By the seventh season, the seasonal carbon flux of both logs and stumps had decreased significantly from prior years. Linear mixed models indicated the variation in the wood inhabiting fungal community composition explained a significant portion of variability in the CO2 flux along with measures of substrate conditions. CO2 flux rates were inversely related to fungal diversity, with logs hosting more species but emitting less CO2 than stumps. Overall, our results suggest that the current treatment of CWD in dynamic forest carbon models may be oversimplified, thereby hampering our ability to predict realistic carbon fluxes associated with wood decomposition.

  17. 氮磷调控及紫云英配施提高早稻冠层特性和产量%Regulation of nitrogen-phosphorus and Chinese milk vetch improve canopy characteristics and yield of early season rice

    Institute of Scientific and Technical Information of China (English)

    时元智; 崔远来; 王力; 才硕; 余双; 刘路广

    2014-01-01

    为揭示不同氮、磷施用量及配合翻压适量紫云英入田对早稻冠层特性和产量的影响,在7个施氮、3个施磷及2个不施氮/磷水平下,开展早稻全生育期叶面积指数LAI、冠层光合有效辐射PAR传输特性、叶片叶绿素SPAD 值、生育后期剑叶净光合速率 Pn及产量的试验观测。结果表明,氮磷调控可显著影响早稻 LAI、叶片叶绿素含量和叶片光合速率,进而通过调节LAI影响冠层PAR传输特性,最终表现为产量上的差异。缺氮对早稻的影响显著高于缺磷,但在施肥充足时,磷肥对产量的影响比氮肥更加显著。早稻冠层特性和产量随氮、磷施用量的增加表现出边际递减效应,当施用量超过某一值时出现拐点,最终表现为产量的下降。在赣抚平原灌区,187.5~225 kg/hm2施氮量和60~120 kg/hm2施磷量以及翻压15000 kg/hm2紫云英鲜草入田可有效提高早稻LAI和冠层PAR截获率In以及叶片叶绿素含量,维持剑叶生长期内较高的净光合速率Pn,获得高产。%Fertilization was an essential agricultural practice to improve soil fertility and quality, and the change leaf area index (LAI) and plant chlorophyll content, and had a direct effect on photosynthetic carbon assimilation and grain yield. In order to reveal the effect of a nitrogen-phosphorus fertilizer regulation and the ploughing down of Chinese milk vetch planted in the winter on the canopy characteristics and yield of early season rice, experiments were carried out, with 7 nitrogen levels (including 2 combined applications of chemical nitrogen and green manure levels) and 3 phosphorus levels and 2 No-nitrogen / phosphorous levels. LAI, the transmission characteristics of canopy photosynthetically active radiation (PAR), and leaf SPAD values were measured during the whole growth period, and the leaf net photosynthetic rate (Pn) was also measured in the heading-flowering period and in the grain

  18. Nitrogen doped carbon nanotubes : synthesis, characterization and catalysis

    NARCIS (Netherlands)

    van Dommele, S.

    2008-01-01

    Nitrogen containing Carbon Nanotubes (NCNT) have altered physical- and chemical properties with respect to polarity, conductivity and reactivity as compared to conventional carbon nanotubes (CNT) and have potential for use in electronic applications or catalysis. In this thesis the incorporation of

  19. Genome-wide patterns of carbon and nitrogen regulation of gene expression validate the combined carbon and nitrogen (CN)-signaling hypothesis in plants

    OpenAIRE

    Palenchar, Peter M; Kouranov, Andrei; Lejay, Laurence V; Coruzzi, Gloria M.

    2004-01-01

    Background Carbon and nitrogen are two signals that influence plant growth and development. It is known that carbon- and nitrogen-signaling pathways influence one another to affect gene expression, but little is known about which genes are regulated by interactions between carbon and nitrogen signaling or the mechanisms by which the different pathways interact. Results Microarray analysis was used to study global changes in mRNA levels due to carbon and nitrogen in Arabidopsis thaliana. An in...

  20. Characterizing spatial and seasonal variability of carbon dioxide and water vapour fluxes above a tropical mixed mangrove forest canopy, India

    Indian Academy of Sciences (India)

    Abhra Chanda; Anirban Akhand; Sudip Manna; Sachinandan Dutta; Sugata Hazra; Indrani Das; V K Dadhwal

    2013-04-01

    The above canopy carbon dioxide and water vapour fluxes were measured by micrometeorological gradient technique at three distant stations, within the world’s largest mangrove ecosystem of Sundarban (Indian part), between April 2011 and March 2012. Quadrat analysis revealed that all the three study sites are characterized by a strong heterogeneity in the mangrove vegetation cover. At day time the forest was a sink for CO2, but its magnitude varied significantly from −0.39 to −1.33 mg m−2 s−1. The station named Jharkhali showed maximum annual fluxes followed by Henry Island and Bonnie Camp. Day time fluxes were higher during March and October, while in August and January the magnitudes were comparatively lower. The seasonal variation followed the same trend in all the sites. The spatial variation of CO2 flux above the canopy was mainly explained by the canopy density and photosynthetic efficiency of the mangrove species. The CO2 sink strength of the mangrove cover in different stations varied in the same way with the CO2 uptake potential of the species diversity in the respective sites. The relationship between the magnitude of day time CO2 uptake by the canopy and photosynthetic photon flux was defined by a non-linear exponential curve (2 ranging from 0.51 to 0.60). Water vapour fluxes varied between 1.4 and 69.5 mg m−2 s−1. There were significant differences in magnitude between day and night time water vapour fluxes, but no spatial variation was observed.

  1. Interactions between leaf nitrogen status and longevity in relation to N cycling in three contrasting European forest canopies

    DEFF Research Database (Denmark)

    Wang, L.; Ibrom, Andreas; Korhonen, J. F. J.;

    2013-01-01

    and Finland, respectively. The objectives were to investigate the distribution of N pools within the canopies of the different forests and to relate this distribution to factors and plant strategies controlling leaf development throughout the seasonal course of a vegetation period. Leaf N pools generally...... of the leaf habit, i.e. deciduous versus evergreen, the majority of the canopy foliage N was retained within the trees. This was accomplished through an effective N re-translocation (beech), higher foliage longevity (fir) or both (boreal pine forest). In combination with data from a literature review...... peak summer canopy N content and also returned the largest amount of N in foliage litter, suggesting that higher N fertility leads to increased turnover in the ecosystem N cycle with higher risks of losses such as leaching and gas emissions....

  2. Interactions between leaf nitrogen status and longevity in relation to N cycling in three contrasting European forest canopies

    DEFF Research Database (Denmark)

    Wang, L.; Ibrom, Andreas; Korhonen, J. F. J.

    2013-01-01

    and Finland, respectively. The objectives were to investigate the distribution of N pools within the canopies of the different forests and to relate this distribution to factors and plant strategies controlling leaf development throughout the seasonal course of a vegetation period. Leaf N pools generally...... peak summer canopy N content and also returned the largest amount of N in foliage litter, suggesting that higher N fertility leads to increased turnover in the ecosystem N cycle with higher risks of losses such as leaching and gas emissions....

  3. δ13C and δ15N of moss Haplocladium microphyllum (Hedw.) Broth. for indicating growing environment variation and canopy retention on atmospheric nitrogen deposition

    Science.gov (United States)

    Liu, Xue-Yan; Xiao, Hua-Yun; Liu, Cong-Qiang; Li, You-Yi

    Mosses have been recognized as a useful tool for biomonitoring atmospheric deposition and assessing regional environment. This study was carried on whether the same moss growing in areas with identical regional atmospheric deposition while under different growing environments would have the same indicating signals. Similar variations in mean δ13C and δ15N signatures were found between mosses collected from five habitats, with an increasing sequence from mosses under canopies to epilithic mosses, indicating that habitats were potentially regulating δ13C and δ15N values of mosses. Dryer habitats (lower water availability) and input of more aerosol N were the main reasons for higher δ13C and δ15N values of mosses at open sites (especially for epilithic species), while more negative values of mosses under canopies were attributed to their wetter habitats and less uptake of aerosol N. Additionally, δ15N values not δ13C varied linearly with canopy thickness from -7.84‰ (1 m) to -4.71±0.7‰ (4 m), suggesting δ15N was more sensitive for indicating canopy retention. Consequently, isotopic data of mosses under different environments could not be compared for atmospheric deposition research with each other even collected at the same site. Moss δ13C and δ15N were affected not only by regional atmospheric N sources but also by their growing environments. δ15N of epilithic Haplocladium microphyllum at open sites can be taken as confident bio-indicator of atmospheric N deposition, which would deepen the application of stable nitrogen isotope of bryophytes in atmosphere-plant system study.

  4. Changes in leaf area, nitrogen content and canopy photosynthesis in soybean exposed to an ozone concentration gradient

    Science.gov (United States)

    Influences of ozone (O3) on light-saturated rates of photosynthesis in crop leaves have been well documented. To increase our understanding of O3 effects on individual- or stand level productivity, a mechanistic understanding of factors determining canopy photosynthesis is necessary. We used a canop...

  5. Phenology, canopy aging and seasonal carbon balance as related to delayed winter pruning of Vitis vinifera L. cv. Sangiovese grapevines

    Directory of Open Access Journals (Sweden)

    Matteo eGatti

    2016-05-01

    Full Text Available Manipulating or shifting annual grapevine growing cycle to offset limitations imposed by global warming is a must today, and delayed winter pruning is a tool to achieve it. However, no information is available about its physiological background, especially in relation to modifications in canopy phenology, demography and seasonal carbon budget. Mechanistic hypothesis underlying this work was that very late winter pruning can achieve significant postponement of phenological stages so that ripening might occur in a cooler period and, concurrently, ripening potential can be improved due to higher efficiency and prolonged longevity of the canopy. Variability in the dynamics of the annual cycle was created in mature potted cv. Sangiovese grapevines subjected to either standard winter pruning (SWP or late and very late winter pruning (LWP, VLWP performed when apical shoots on the unpruned canes were at the stage of 2 and 7 unfolded leaves. Vegetative growth, phenology and canopy net CO2 exchange (NCER was followed throughout the season.Despite LWP and VLWP induced a bud-burst delay of 17 and 31 days vs. SWP, the delay was fully offset at harvest for LWP and was reduced to 6 days in VLWP. LWP showed notably higher canopy efficiency as shorter time needed to reach maximum NCER/leaf area (22 days vs 34 in SWP, highest maximum NCER/leaf area (+37% as compared to SWP and higher NCER/leaf area rates from veraison to end of season. As a result, seasonal cumulated carbon in LWP was 17% higher than SWP. A negative functional relationship was also established between amount of leaf area removed at winter pruning and yield per vine and berry number per cluster. Although retarded winter pruning was not able to postpone late-season phenological stages under the warm conditions of this study, it showed a remarkable potential to limit yield while improving grape quality, thereby fostering the hypothesis that it could be used to replace time-consuming and costly

  6. Phenology, Canopy Aging and Seasonal Carbon Balance as Related to Delayed Winter Pruning of Vitis vinifera L. cv. Sangiovese Grapevines.

    Science.gov (United States)

    Gatti, Matteo; Pirez, Facundo J; Chiari, Giorgio; Tombesi, Sergio; Palliotti, Alberto; Merli, Maria C; Poni, Stefano

    2016-01-01

    Manipulating or shifting annual grapevine growing cycle to offset limitations imposed by global warming is a must today, and delayed winter pruning is a tool to achieve it. However, no information is available about its physiological background, especially in relation to modifications in canopy phenology, demography and seasonal carbon budget. Mechanistic hypothesis underlying this work was that very late winter pruning (LWP) can achieve significant postponement of phenological stages so that ripening might occur in a cooler period and, concurrently, ripening potential can be improved due to higher efficiency and prolonged longevity of the canopy. Variability in the dynamics of the annual cycle was created in mature potted cv. Sangiovese grapevines subjected to either standard winter pruning (SWP) or late and very late winter pruning (LWP, VLWP) performed when apical shoots on the unpruned canes were at the stage of 2 and 7 unfolded leaves. Vegetative growth, phenology and canopy net CO2 exchange (NCER) were followed throughout the season. Despite LWP and VLWP induced a bud-burst delay of 17 and 31 days vs. SWP, the delay was fully offset at harvest for LWP and was reduced to 6 days in VLWP. LWP showed notably higher canopy efficiency as shorter time needed to reach maximum NCER/leaf area (22 days vs. 34 in SWP), highest maximum NCER/leaf area (+37% as compared to SWP) and higher NCER/leaf area rates from veraison to end of season. As a result, seasonal cumulated carbon in LWP was 17% higher than SWP. A negative functional relationship was also established between amount of leaf area removed at winter pruning and yield per vine and berry number per cluster. Although retarded winter pruning was not able to postpone late-season phenological stages under the warm conditions of this study, it showed a remarkable potential to limit yield while improving grape quality, thereby fostering the hypothesis that it could be used to replace time-consuming and costly cluster

  7. XPS of nitrogen-containing functional groups on activated carbon

    NARCIS (Netherlands)

    Jansen, R.J.J.; Bekkum, van H.

    1995-01-01

    XPS is used to study the binding energy of the Cls, Nls and Ols photoelectrons of surface groups on several nitrogen-containing activated carbons. Specific binding energies are assigned to amide (399.9 eV). lactam and imidc (399.7 eV). pyridine (398.7 eV), pyrrole (400.7 eV), alkylamine. secondary a

  8. Nitrogen, carbon, and sulfur metabolism in natural Thioploca samples

    DEFF Research Database (Denmark)

    Otte, S.; Kuenen, JG; Nielsen, LP

    1999-01-01

    Filamentous sulfur bacteria of the genus Thioploca occur as dense mats on the continental shelf off the coast of Chile and Peru. Since little is known about their nitrogen, sulfur, and carbon metabolism, this study was undertaken to investigate their (eco)physiology. Thioploca is able to store in...

  9. Intercropping enhances soil carbon and nitrogen

    NARCIS (Netherlands)

    Cong, W.; Hoffland, E.; Li, L.; Six, J.; Sun, J.H.; Bao, X.G.; Zhang, F.S.; Werf, van der W.

    2015-01-01

    Intercropping, the simultaneous cultivation of multiple crop species in a single field, increases aboveground productivity due to species complementarity. We hypothesized that intercrops may have greater belowground productivity than sole crops, and sequester more soil carbon over time due to greate

  10. Effects of Nitrogen Forms on Carbon and Nitrogen Accumulation in Tomato Seedling

    Institute of Scientific and Technical Information of China (English)

    GE Ti-da; SONG Shi-wei; CHI Ming-han; HUANG Dan-feng; K Iwasaki

    2008-01-01

    Utilization of organic nitrogen (N) is an important aspect of plant N assimilation and has potential application in sustainable agriculture. The aim of this study was to investigate the plant growth, C and N accumulation in leaves and roots of tomato seedlings in response to inorganic (NH4+-N, NO3--N) and organic nitrogen (Gly-N). Different forms of nitrogen (NH4+-N, NO3--N, Gly-N) were supplied to two tomato cultivars (Shenfen 918 and Huying 932) using a hydroponics system. The plant dry biomass, chlorophyll content, root activity, total carbon and nitrogen content in roots and leaves, and total N absorption, etc. were assayed during the cultivation. Our results showed that no significant differences in plant height, dry biomass, and total N content were found within the first 16 d among three treatments; however, significant differences in treatments on 24 d and 32 d were observed, and the order was NO3--N > GIy-N > NH4+-N. Significant differences were also observed between the two tomato cultivars. Chlorophyll contents in the two cultivars were significantly increased by the GIy-N treatment, and root activity showed a significant decrease in NH4+-N treatment. Tomato leaf total carbon content was slightly affected by different N forms; however, total carbon in root and total nitrogen in root and leaf were promoted significantly by inorganic and organic N. Among the applied N forms, the increasing effects of the NH4+-N treatment were larger than that of the Gly-N. In a word, different N resources resulted in different physiological effects in tomatoes. Organic nitrogen (e.g., Gly-N) can be a proper resource of plant N nutrition. Tomatoes of different genotypes had different responses under organic nitrogen (e.g., Gly-N) supplies.

  11. Carbon and nitrogen budgets of the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Somasundar, K.; Rajendran, A.; DileepKumar, M.; SenGupta, R.

    grams (Tg) for carbon, and 8.06 and 3.60 Tg for nitrogen, respectively. The carbon budget was found to be negatively balanced by 84 Tg year- t. A possible source to compensate for this deficit could be from the northward movement of Antarctic Bottom... with adjoining seas and rivers. This in turn affects the nutrient dynamics of both the Arabian Sea and the Red Sea. Bethoux ( 1988 ) further emphasized the importance of the effect of deep outflow of materials (carbon, nutrients and oxygen) from the Red Sea...

  12. Influence of stocking, site quality, stand age, low-severity canopy disturbance, and forest composition on sub-boreal aspen mixedwood carbon stocks

    Science.gov (United States)

    Reinikainen, Michael; D’Amato, Anthony W.; Bradford, John B.; Fraver, Shawn

    2014-01-01

    Low-severity canopy disturbance presumably influences forest carbon dynamics during the course of stand development, yet the topic has received relatively little attention. This is surprising because of the frequent occurrence of such events and the potential for both the severity and frequency of disturbances to increase as a result of climate change. We investigated the impacts of low-severity canopy disturbance and average insect defoliation on forest carbon stocks and rates of carbon sequestration in mature aspen mixedwood forests of varying stand age (ranging from 61 to 85 years), overstory composition, stocking level, and site quality. Stocking level and site quality positively affected the average annual aboveground tree carbon increment (CAAI), while stocking level, site quality, and stand age positively affected tree carbon stocks (CTREE) and total ecosystem carbon stocks (CTOTAL). Cumulative canopy disturbance (DIST) was reconstructed using dendroecological methods over a 29-year period. DIST was negatively and significantly related to soil carbon (CSOIL), and it was negatively, albeit marginally, related to CTOTAL. Minima in the annual aboveground carbon increment of trees (CAI) occurred at sites during defoliation of aspen (Populus tremuloides Michx.) by forest tent caterpillar (Malacosoma disstria Hubner), and minima were more extreme at sites dominated by trembling aspen than sites mixed with conifers. At sites defoliated by forest tent caterpillar in the early 2000s, increased sequestration by the softwood component (Abies balsamea (L.) Mill. and Picea glauca (Moench) Voss) compensated for overall decreases in CAI by 17% on average. These results underscore the importance of accounting for low-severity canopy disturbance events when developing regional forest carbon models and argue for the restoration and maintenance of historically important conifer species within aspen mixedwoods to enhance stand-level resilience to disturbance agents and maintain

  13. Moderate water stress from regulated deficit irrigation decreases transpiration similarly to net carbon exchange in grapevine canopies

    Science.gov (United States)

    To determine the effects of timing and extent of regulated deficit irrigation (RDI) on grapevine (Vitis vinifera) canopies, whole-canopy transpiration (TrV) and canopy conductance to water vapor (gc) were calculated from whole-vine gas exchange near key stages of fruit development. The vines were ma...

  14. Simultaneous tracing of carbon and nitrogen isotopes in human cells.

    Science.gov (United States)

    Nilsson, Roland; Jain, Mohit

    2016-05-24

    Stable isotope tracing is a powerful method for interrogating metabolic enzyme activities across the metabolic network of living cells. However, most studies of mammalian cells have used (13)C-labeled tracers only and focused on reactions in central carbon metabolism. Cellular metabolism, however, involves other biologically important elements, including nitrogen, hydrogen, oxygen, phosphate and sulfur. Tracing stable isotopes of such elements may help shed light on poorly understood metabolic pathways. Here, we demonstrate the use of high-resolution mass spectrometry to simultaneously trace carbon and nitrogen metabolism in human cells cultured with (13)C- and (15)N-labeled glucose and glutamine. To facilitate interpretation of the complex isotopomer data generated, we extend current methods for metabolic flux analysis to handle multivariate mass isotopomer distributions (MMIDs). We find that observed MMIDs are broadly consistent with known biochemical pathways. Whereas measured (13)C MIDs were informative for central carbon metabolism, (15)N isotopes provided evidence for nitrogen-carrying reactions in amino acid and nucleotide metabolism. This computational and experimental methodology expands the scope of metabolic flux analysis beyond carbon metabolism, and may prove important to understanding metabolic phenotypes in health and disease.

  15. A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes

    Science.gov (United States)

    Naudts, K.; Ryder, J.; McGrath, M. J.; Otto, J.; Chen, Y.; Valade, A.; Bellasen, V.; Berhongaray, G.; Bönisch, G.; Campioli, M.; Ghattas, J.; De Groote, T.; Haverd, V.; Kattge, J.; MacBean, N.; Maignan, F.; Merilä, P.; Penuelas, J.; Peylin, P.; Pinty, B.; Pretzsch, H.; Schulze, E. D.; Solyga, D.; Vuichard, N.; Yan, Y.; Luyssaert, S.

    2015-07-01

    Since 70 % of global forests are managed and forests impact the global carbon cycle and the energy exchange with the overlying atmosphere, forest management has the potential to mitigate climate change. Yet, none of the land-surface models used in Earth system models, and therefore none of today's predictions of future climate, accounts for the interactions between climate and forest management. We addressed this gap in modelling capability by developing and parametrising a version of the ORCHIDEE land-surface model to simulate the biogeochemical and biophysical effects of forest management. The most significant changes between the new branch called ORCHIDEE-CAN (SVN r2290) and the trunk version of ORCHIDEE (SVN r2243) are the allometric-based allocation of carbon to leaf, root, wood, fruit and reserve pools; the transmittance, absorbance and reflectance of radiation within the canopy; and the vertical discretisation of the energy budget calculations. In addition, conceptual changes were introduced towards a better process representation for the interaction of radiation with snow, the hydraulic architecture of plants, the representation of forest management and a numerical solution for the photosynthesis formalism of Farquhar, von Caemmerer and Berry. For consistency reasons, these changes were extensively linked throughout the code. Parametrisation was revisited after introducing 12 new parameter sets that represent specific tree species or genera rather than a group of often distantly related or even unrelated species, as is the case in widely used plant functional types. Performance of the new model was compared against the trunk and validated against independent spatially explicit data for basal area, tree height, canopy structure, gross primary production (GPP), albedo and evapotranspiration over Europe. For all tested variables, ORCHIDEE-CAN outperformed the trunk regarding its ability to reproduce large-scale spatial patterns as well as their inter

  16. A vertically discretised canopy description for ORCHIDEE (SVN r2290 and the modifications to the energy, water and carbon fluxes

    Directory of Open Access Journals (Sweden)

    K. Naudts

    2014-12-01

    Full Text Available Since 70% of global forests are managed and forests impact the global carbon cycle and the energy exchange with the overlying atmosphere, forest management has the potential to mitigate climate change. Yet, none of the land surface models used in Earth system models, and therefore none of today's predictions of future climate, account for the interactions between climate and forest management. We addressed this gap in modelling capability by developing and parametrizing a version of the land surface model ORCHIDEE to simulate the biogeochemical and biophysical effects of forest management. The most significant changes between the new branch called ORCHIDEE-CAN (SVN r2290 and the trunk version of ORCHIDEE (SVN r2243 are the allometric-based allocation of carbon to leaf, root, wood, fruit and reserve pools; the transmittance, absorbance and reflectance of radiation within the canopy; and the vertical discretisation of the energy budget calculations. In addition, conceptual changes towards a~better process representation occurred for the interaction of radiation with snow, the hydraulic architecture of plants, the representation of forest management and a~numerical solution for the photosynthesis formalism of Farquhar, von Caemmerer and Berry. For consistency reasons, these changes were extensively linked throughout the code. Parametrization was revisited after introducing twelve new parameter sets that represent specific tree species or genera rather than a group of unrelated species, as is the case in widely used plant functional types. Performance of the new model was compared against the trunk and validated against independent spatially explicit data for basal area, tree height, canopy strucure, GPP, albedo and evapotranspiration over Europe. For all tested variables ORCHIDEE-CAN outperformed the trunk regarding its ability to reproduce large-scale spatial patterns as well as their inter-annual variability over Europe. Depending on the data

  17. Short-term changes in carbon isotope composition of soluble carbohydrates and starch: from canopy leaves to the root system.

    Science.gov (United States)

    Göttlicher, Sabine; Knohl, Alexander; Wanek, Wolfgang; Buchmann, Nina; Richter, Andreas

    2006-01-01

    Changes in the 13C discrimination of current leaf photosynthesis might have profound impacts on root respiratory substrates. Therefore, the aim of this study was (1) to refine a method for the isolation of root and leaf starch and soluble sugars (neutral fraction) for stable carbon isotope analysis and (2) to assess the short-term temporal variability of the C isotope composition (delta13C) of starch and of the neutral fraction of beech roots and leaves at different canopy heights. An existing method for isolating starch for stable C isotope analysis based on enzymatic hydrolysis was modified to account for the low starch content of the samples. This was achieved by removing the enzyme (alpha-amylase) by ultrafiltration after the hydrolysis, resulting in very low carbon blanks. The neutral fraction was separated from organic acids and cations by ion-exchange chromatography. An anion-exchange resin in the [HCO3]--form was chosen that ensured high precision of C blanks. Beech leaves at 5, 10 and 20 m above the forest floor as well as roots were sampled six times during a day/night cycle in July 2003. Delta13C values of bulk material, starch and the neutral fraction increased from the lower to the higher canopy with mean differences between 5 and 20 m of 3.8, 3.4 and 2.7 per thousand for the delta13C values of starch, neutral fraction and bulk foliage, respectively. The delta13C value of foliar starch increased from the morning to the afternoon and decreased during the night, but diurnal differences (up to 3.1 per thousand) were only statistically significant for leaves sampled at 5 and 10 m height. In roots, no diurnal variation in the delta13C of starch was observed during the short time frame of one day and the delta13C of the neutral fraction did not differ between samples taken at 16:30 and 22:00. Calculated delta13C values of starch, which was mobilised during the night, were more positive than the total starch (all sampling times pooled) in leaves. Furthermore

  18. Interactive effects of nitrogen fertilization and irrigation on grain yield, canopy temperature, and nitrogen use efficiency in overhead sprinkler-irrigated Durum Wheat

    Science.gov (United States)

    Nitrogen and irrigation management are crucial in the production of high protein irrigated durum wheat (Triticum durum Desf.) in arid regions. However, as the availability of irrigation water decreases and potential costs and regulation of nitrogen (N) increase, there is a need to understand how ir...

  19. [Interactions of straw, nitrogen fertilizer and bacterivorous nematodes on soil labile carbon and nitrogen and greenhouse gas emissions].

    Science.gov (United States)

    Zhang, Teng-Hao; Wang, Nan; Liu, Man-Qiang; Li, Fang-Hui; Zhu, Kang-Li; Li, Hui-Xin; Hu, Feng

    2014-11-01

    A 3 x 2 factorial design of microcosm experiment was conducted to investigate the interactive effects of straw, nitrogen fertilizer and bacterivorous nematodes on soil microbial biomass carbon (C(mic)) and nitrogen (N(mic)), dissolved organic carbon (DOC) and nitrogen (DON), mineral nitrogen (NH(4+)-N and NO(3-)-N), and greenhouse gas (CO2, N2O and CH4) emissions. Results showed that straw amendment remarkably increased the numbers of bacterivorous nematodes and the contents of Cmic and Nmic, but Cmic and Nmic decreased with the increasing dose of nitrogen fertilization. The effects of bacterivorous nematodes strongly depended on either straw or nitrogen fertilization. The interactions of straw, nitrogen fertilization and bacterivorous nematodes on soil DOC, DON and mineral nitrogen were strong. Straw and nitrogen fertilization increased DOC and mineral nitrogen contents, but their influences on DON depended on the bacterivorous nematodes. The DOC and mineral nitrogen were negatively and positively influenced by the bacterivorous nematodes, re- spectively. Straw significantly promoted CO2 and N2O emissions but inhibited CH4 emission, while interactions between nematodes and nitrogen fertilization on emissions of greenhouse gases were obvious. In the presence of straw, nematodes increased cumulative CO2 emissions with low nitrogen fertilization, but decreased CO2 and N2O emissions with high nitrogen fertilization on the 56th day after incubation. In summary, mechanical understanding the soil ecological process would inevitably needs to consider the roles of soil microfauna.

  20. Synthesis and characterization of well-aligned carbon nitrogen nanotubes by microwave plasma chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Well-aligned carbon nitrogen nanotube films have been synthesized successfully on mesoporous silica substrates by microwave plasma chemical vapor deposition (MWPCVD) method. Studies on their morphology, structure, and composition by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX), respectively, indicate that these nanotubes consist of linearly polymerized carbon nitrogen nanobells, and the nitrogen atoms have been doped into carbon netweork to form a new structure C1-xNx (x=0.16±0.01). X-ray photoelectron spectroscopy (XPS) results of the samples further demonstrate that carbon bonds covalently with nitrogen in all the carbon nitrogen nanotube films.

  1. Transesterification of triglycerides using nitrogen-functionalized carbon nanotubes.

    Science.gov (United States)

    Villa, Alberto; Tessonnier, Jean-Philippe; Majoulet, Olivier; Su, Dang Sheng; Schlögl, Robert

    2010-02-22

    Nitrogen-functionalized carbon nanotubes were synthesized by grafting amino groups to the surface of the nanotubes. The nanotubes exhibited promising results in the base-catalyzed liquid phase transesterification of glyceryl tributyrate with methanol, which is a model reaction for the production of biodiesel. The concentration of the active sites and the reaction parameters, such as temperature and glyceryl tributyrate to methanol ratio, were shown to significantly affect catalytic performance. The grafting technique employed allowed for design and control of the active sites. As a consequence, it was possible to design a nitrogen-functionalized carbon nanotube catalyst with a few strong, basic groups. This might be of interest for carbohydrate conversion reactions where strong basic sites are required but the pH of the solution should remain mild to avoid the degradation of the reactants and/or products.

  2. On The Cosmic Origins Of Carbon And Nitrogen

    CERN Document Server

    Henry, R B C; Köppen, J

    2000-01-01

    We analyze the behavior of N/O and C/O abundance ratios as a function of metallicity as gauged by O/H in large, extant Galactic and extragalactic H II region abundance samples. Numerical chemical evolution models are computed using published stellar yields implied by comparing analytical models to the observations. Our results suggest that carbon and nitrogen originate from separate production sites and are decoupled from one another. Massive stars (M>8M_sun) dominate the production of carbon, while intermediate-mass stars between 4 and 8 solar masses, with a characteristic ejection delay time of 250 Myr after their formation, dominate nitrogen production. Carbon production is positively sensitive to metallicity through mass loss processes in massive stars and has a pseudo-secondary character. Nitrogen production in intermediate mass stars is primary at low metallicity, but clearly secondary (and perhaps tertiary) when 12+log(O/H)>8.3. The observed flat behavior of N/O versus O/H in metal-poor galaxies is exp...

  3. Effect of grazing and canopy on Mediterranean ecosystem functioning: Carbon dioxide exchange and the dynamics of carbon and nutrient pools

    Science.gov (United States)

    Mirzaei, Heydar; Tenhunen, John; Hossein, Zaman; Li, Yuelin; Otieno, Dennis

    2010-05-01

    Mediterranean ecosystems occupy less than 5 % of the Earth's surface, yet they contain about 20 % of the world's flora, including important components in grasslands. In this study, important ecosystem functions (CO2 exchange, biomass production and nutrient uptake of the herbaceous layer of a Mediterranean grassland ecosystem) at Herdade da Mitra, in Portugal were studied. The main objectives of this project were, to understand effects of grazing and canopy layer (overstory) on ecosystem functioning respectively. The canopy layer consists of some woody species mainly Quercus ilex and Qu. Suber. Results showed that trees added considerable amounts of nutrients to the soil beneath their canopies, and had the potential to facilitate understory production. Although there was no significant difference in total biomass accumulation between understory and open locations. Analysis of soil N concentration revealed higher soil N under the trees when compared to those in open areas. Although NEE was limited by light intensity in the understory, model projection of GPP showed no difference between the understory and the open locations in their potential assimilatory capacity but depending on the locations (open vs understory), grazing influenced CO2 exchange processes differently. We found no significant differences in GPP between grazed and ungrazed sites in the open locations, while large differences occurred in the understory, with lower NEE in the grazed as compared to the ungrazed locations. Significant differences, however, occurred between the two locations in ecosystem respiration, showing higher respiration in grazed location in the open site while in the understory site respiration was similar in both grazed and ungrazed locations. Foliar N concentration in understory and open sites showed a different pattern, as the ungrazed location in the understory indicated lower values compared to grazed locations, although in the open sites, ungrazed locations exhibited larger

  4. A 6-year-long manipulation with soil warming and canopy nitrogen additions does not affect xylem phenology and cell production of mature black spruce

    Directory of Open Access Journals (Sweden)

    Madjelia Cangre Ebou eDAO

    2015-11-01

    Full Text Available The predicted climate warming and increased atmospheric inorganic nitrogen deposition are expected to have dramatic impacts on plant growth. However, the extent of these effects and their interactions remains unclear for boreal forest trees. The aim of this experiment was to investigate the effects of increased soil temperature and nitrogen (N depositions on stem intra-annual growth of two mature stands of black spruce [Picea mariana (Mill. BSP] in Quebec, Canada. During 2008-2013, the soil around mature trees was warmed up by 4 °C with heating cables during the growing season and precipitations containing three times the current inorganic N concentration were added by frequent canopy applications. Xylem phenology and cell production were monitored weekly from April to October. The 6-year-long experiment performed in two sites at different altitude showed no substantial effect of warming and N-depositions on xylem phenological phases of cell enlargement, wall thickening and lignification. Cell production, in terms of number of tracheids along the radius, also did not differ significantly and followed the same patterns in control and treated trees. These findings allowed the hypothesis of a medium-term effect of soil warming and N depositions on the growth of mature black spruce to be rejected.

  5. Carbon and Nitrogen Accumulation Rates in Salt Marshes in Oregon, USA

    Science.gov (United States)

    Two important ecosystem services of wetlands are carbon sequestration and filtration of nutrients and particulates. We quantified the carbon and nitrogen accumulation rates in salt marshes at 135 plots distributed across eight estuaries located in Oregon, USA. Net carbon and ...

  6. Interactions between leaf nitrogen status and longevity in relation to N cycling in three contrasting European forest canopies

    DEFF Research Database (Denmark)

    Wang, L.; Ibrom, Andreas; Korhonen, J. F. J.;

    2013-01-01

    Seasonal and spatial variations in foliar nitrogen (N) parameters were investigated in three European forests with different tree species, viz. beech (Fagus sylvatica L.), Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and Scots pine (Pinus sylvestris L.) growing in Denmark, the Netherlands...

  7. Remarkably efficient synthesis of 2H-indazole 1-oxides and 2H-indazoles via tandem carbon-carbon followed by nitrogen-nitrogen bond formation.

    Science.gov (United States)

    Bouillon, Isabelle; Zajícek, Jaroslav; Pudelová, Nadĕzda; Krchnák, Viktor

    2008-11-21

    Base-catalyzed tandem carbon-carbon followed by nitrogen-nitrogen bond formations quantitatively converted N-alkyl-2-nitro-N-(2-oxo-2-aryl-ethyl)-benzenesulfonamides to 2H-indazoles 1-oxides under mild conditions. Triphenylphosphine or mesyl chloride/triethylamine-mediated deoxygenation afforded 2H-indazoles.

  8. Sewage sludge composting simulation as carbon/nitrogen concentration change

    Institute of Scientific and Technical Information of China (English)

    Nassereldeen Kabbashi

    2011-01-01

    Available composting models do not describe accurately the dynamics of composting processes.Difficulty in modeling composting processes is attributed mainly to the unpredicted change in process rate caused by change in activation energy value (E).This article presented the results of an attempt made to utilize patterns of change in carbon,nitrogen and temperature profiles to model sewage sludge composting process as a multi-stage process.Results of controlled sewage sludge composting experiments were used in th estudy.All the experiments were carried out as batch experiments in a 300-liter Horizontal Drum Bioreactor (HDB).Analysis of the profiles of carbon,nitrogen and temperature has indicated that there were clear patterns that could be used to develop simple models of the process,the initial C/N ratio was between 7-8 and the final C/N ratio of the compost in most experiments were found to be around 15.0,indicating the compost was fully matured and could be used safely for agricultural purpose.Electrical conductivity of composting material decreased from 1.83 to 1.67 dS/m,after a period,it increased gradually from 2.01 to 2.23 dS/m and remained at around 2.33 dS/m till the end of composting.It is found that change in the concentration of total carbon can reasonably be described by three constant process rate coefficients (k1,k2,k3).It is found that the process starts with a certain process rate coefficient (k1) and continues until peak temperature is reached,then it reaches lower process (k2) in the declining phase of the thermophilic stage,and finally it proceeds with a faster process rate (k3) when maturation is reached.Change in the concentration of total nitrogen has shown to have the same patterns of change as carbon.

  9. Nitrogen Doped Carbon Nanotubes from Organometallic Compounds: A Review

    Directory of Open Access Journals (Sweden)

    Neil J. Coville

    2010-03-01

    Full Text Available Nitrogen doped carbon nanotubes (N-CNTs have become a topic of increased importance in the study of carbonaceous materials. This arises from the physical and chemical properties that are created when N is embedded in a CNT. These properties include modified chemical reactivity and modified conductivity and mechanical properties. A range of methodologies have been devised to synthesize N-CNTs. One of the procedures uses a floating catalyst in which an organometallic complex is decomposed in the gas phase in the presence of a nitrogen containing reactant to give N-CNTs. Most studies have been limited to ferrocene, ring substituted ferrocene and Fe(CO5. This review covers the synthesis (and properties of N-CNTs and other shaped carbon nanomaterials (SCNMs produced using organometallic complexes. It summarizes the effects that physical parameters such as temperature, pressure, gas flow rates, type and concentration of N source etc. have on the N-CNT type, size and yields as well as the nitrogen content incorporated into the tubes that are produced from organometallic complexes. Proposed growth models for N-CNT synthesis are also reported.

  10. Spatial Variability Analysis of Within-Field Winter Wheat Nitrogen and Grain Quality Using Canopy Fluorescence Sensor Measurements

    OpenAIRE

    Xiaoyu Song; Guijun Yang; Chenghai Yang; Jihua Wang; Bei Cui

    2017-01-01

    Wheat grain protein content (GPC) is a key component when evaluating wheat nutrition. It is also important to determine wheat GPC before harvest for agricultural and food process enterprises in order to optimize the wheat grading process. Wheat GPC across a field is spatially variable due to the inherent variability of soil properties and position in the landscape. The objectives of this field study were: (i) to assess the spatial and temporal variability of wheat nitrogen (N) attributes rela...

  11. The carbon-nitrogen balance of the nodule and its regulation under elevated carbon dioxide concentration.

    Science.gov (United States)

    Libault, Marc

    2014-01-01

    Legumes have developed a unique way to interact with bacteria: in addition to preventing infection from pathogenic bacteria like any other plant, legumes also developed a mutualistic symbiotic relationship with one gender of soil bacteria: rhizobium. This interaction leads to the development of a new root organ, the nodule, where the differentiated bacteria fix for the plant the atmospheric dinitrogen (atmN2). In exchange, the symbiont will benefit from a permanent source of carbon compounds, products of the photosynthesis. The substantial amounts of fixed carbon dioxide dedicated to the symbiont imposed to the plant a tight regulation of the nodulation process to balance carbon and nitrogen incomes and outcomes. Climate change including the increase of the concentration of the atmospheric carbon dioxide is going to modify the rates of plant photosynthesis, the balance between nitrogen and carbon, and, as a consequence, the regulatory mechanisms of the nodulation process. This review focuses on the regulatory mechanisms controlling carbon/nitrogen balances in the context of legume nodulation and discusses how the change in atmospheric carbon dioxide concentration could affect nodulation efficiency.

  12. Science Letters: Nitrogen doping of activated carbon loading Fe2O3 and activity in carbon-nitric oxide reaction

    Institute of Scientific and Technical Information of China (English)

    WAN Xian-kai; ZOU Xue-quan; SHI Hui-xiang; WANG Da-hui

    2007-01-01

    Nitrogen doping of activated carbon loading Fe2O3 was performed by annealing in ammonia, and the activity of the modified carbon for NO reduction was studied in the presence of oxygen. Results show that Fe2O3 enhances the amount of surface oxygen complexes and facilitates nitrogen incorporation in the carbon, especially in the form of pyridinic nitrogen. The modified carbon shows excellent activity for NO reduction in the low temperature regime (<500 ℃) because of the cooperative effect of Fe2O3 and the surface nitrogen species.

  13. Permafrost carbon-climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics.

    Science.gov (United States)

    Koven, Charles D; Lawrence, David M; Riley, William J

    2015-03-24

    Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon-nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost region is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. Although nitrogen dynamics are highly uncertain, the future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw.

  14. Integration of Carbon, Nitrogen, and Oxygen Metabolism in Escherichia coli

    Science.gov (United States)

    2012-10-22

    glycolysis and the  citric   acid   cycle  and monitored the effect on RpoS degradation  in vivo. Nutrient  upshifts trigger RpoS degradation  independently...Yuan  et  al.,  2009). We  successfully combined the simplified nitrogen assimilation model with simplified models of glycolysis and the  TCA  cycle  to...TCA  cycle  (where carbon and nitrogen metabolism directly intersect). Our  investigation  yielded  significant  advances  in  the  understanding  of  E

  15. Dynamics of carbon, nitrogen and phosphorus in soil amended with irradiated, pasteurized and limed biosolids.

    Science.gov (United States)

    Franco-Hernández, Olivia; Mckelligan-Gonzalez, Alba Natalia; Lopez-Olguin, Ana Maria; Espinosa-Ceron, Fabiola; Escamilla-Silva, Eleazar; Dendooven, Luc

    2003-03-01

    Sewage biosolids contain high concentrations of pathogens, which limits their use as soil amendment. This study investigated how application of lime (Ca(OH)2), irradiation, or pasteurization reduced pathogens in biosolids and how its application affected soil characteristics. A soil sampled outside the canopy of Mesquite trees (Prosopis laevigata) and from a pasture at Lerma (Mexico) was amended with treated or untreated biosolids, characterized and incubated aerobically while dynamics of carbon (C), nitrogen (N) and phosphorus (P) were monitored. Heavy metals concentrations in the biosolids were low, so it was of excellent quality (USEPA). The amount of pathogens in the biosolids made it a class "B" (USEPA) which can be used in forests. Only irradiation sufficiently reduced faecal coliforms to make it a class "A" biosolids without restrictions in application. C mineralization increased significantly when biosolids were added, but not concentrations of available P (P < 0.05). Ammonium (NH4+) concentrations in soil amended with biosolids were higher compared to unamended soil, but not the concentrations of nitrate (NO3-) except when biosolids treated with Ca(OH)2 was added to the Lerma soil.

  16. Long-term effect of tillage, nitrogen fertilization and cover crops on soil organic carbon and total nitrogen content

    OpenAIRE

    2011-01-01

    Metadata only record No-till practices, in conjunction with cover crops and nitrogen fertilization, have been shown to augment soil organic carbon content and total nitrogen content. However, interactions between these components in a no-till system are not well-known. This study offers a long-term (1993-2008) comparative analysis of conventional versus no-till practices as well as a some insight regarding the synergies between no-till, nitrogen fertilization, and cover crops. Maize, wheat...

  17. Carbon-to-nitrogen ratios in agricultural residues

    Energy Technology Data Exchange (ETDEWEB)

    Ilukor, J.O.; Oluka, S.O. [Department of Physics, Makerere University, Kampala (Uganda)

    1995-12-31

    Agronomic crop residues produce greenhouse gas emissions. Crops that produce residues at harvest and during processing may vary from country to country. These residues, which can be in the form of peels, husks, stalks, or straw, are generally considered to be waste products. The carbon (C) and nitrogen (N) content of 19 different agronomic and grass crops common in Uganda were determined using standard laboratory methods. The C and N content of the samples were calculated from two separate equations containing a moisture correction factor. The crop residue C/N ratios were similar to UNEP/OECD/IEA/IPCC values. 3 tabs., 7 refs.

  18. Nitrogen-doped porous carbon from Camellia oleifera shells with enhanced electrochemical performance.

    Science.gov (United States)

    Zhai, Yunbo; Xu, Bibo; Zhu, Yun; Qing, Renpeng; Peng, Chuan; Wang, Tengfei; Li, Caiting; Zeng, Guangming

    2016-04-01

    Nitrogen doped porous activated carbon was prepared by annealing treatment of Camellia oleifera shell activated carbon under NH3. We found that nitrogen content of activated carbon up to 10.43 at.% when annealed in NH3 at 800 °C. At 600 °C or above, the N-doped carbon further reacts with NH3, leads to a low surface area down to 458 m(2)/g and low graphitization degree. X-ray photoelectron spectroscope (XPS) analysis indicated that the nitrogen functional groups on the nitrogen-doped activated carbons (NACs) were mostly in the form of pyridinic nitrogen. We discovered that the oxygen groups and carbon atoms at the defect and edge sites of graphene play an important role in the reaction, leading to nitrogen atoms incorporated into the lattice of carbon. When temperatures were lower than 600 °C the nitrogen atoms displaced oxygen groups and formed nitrogen function groups, and when temperatures were higher than 600 °C and ~4 at.% carbon atoms and part of oxygen function groups reacted with NH3. When compared to pure activated carbon, the nitrogen doped activated carbon shows nearly four times the capacitance (191 vs 51 F/g).

  19. Efficient Boron-Carbon-Nitrogen Nanotube Formation Via Combined Laser-Gas Flow Levitation

    Science.gov (United States)

    Whitney, R. Roy (Inventor); Jordan, Kevin (Inventor); Smith, Michael W. (Inventor)

    2015-01-01

    A process for producing boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula BxCyNz. The process utilizes a combination of laser light and nitrogen gas flow to support a boron ball target during heating of the boron ball target and production of a boron vapor plume which reacts with nitrogen or nitrogen and carbon to produce boron nitride nanotubes and/or boron-carbon-nitrogen nanotubes of the general formula BxCyNz.

  20. Determinism of carbon and nitrogen reserve accumulation in legume seeds.

    Science.gov (United States)

    Munier-Jolain, Nathalie; Larmure, Annabelle; Salon, Christophe

    2008-10-01

    In legume plants, the determination of individual seed weight is a complex phenomenon that depends on two main factors. The first one corresponds to the number of cotyledon cells, which determines the potential seed weight as the cotyledon cell number is related to seed growth rate during seed filling. Since cell divisions take place between flowering and the beginning of seed filling, any stress occurring before the beginning of seed filling can affect individual seed growth rate (C and N reserve accumulation in seeds), and thus individual seed weights. The second factor concerns carbon and nitrogen supply to the growing seed to support reserve accumulation. Grain legume species produce protein-rich seeds involving high requirement of nitrogen. Since seed growth rate as determined by cotyledon cell number is hardly affected by photoassimilate availability during the filling period, a reduction of photosynthetic activity caused by nitrogen remobilization in leaves (e.g., remobilization of essential proteins involved in photosynthesis) can lead to shorten the duration of the filling period, and by that can provoke a limitation of individual seed weights. Accordingly, any biotic or abiotic stress during seed filling causing a decrease in photosynthetic activity should lead to a reduction of the duration of seed filling.

  1. Gap locations influence the release of carbon, nitrogen and phosphorus in two shrub foliar litter in an alpine fir forest.

    Science.gov (United States)

    He, Wei; Wu, Fuzhong; Yang, Wanqin; Zhang, Danju; Xu, Zhenfeng; Tan, Bo; Zhao, Yeyi; Justine, Meta Francis

    2016-02-24

    Gap formation favors the growth of understory plants and affects the decomposition process of plant debris inside and outside of gaps. Little information is available regarding how bioelement release from shrub litter is affected by gap formation during critical periods. The release of carbon (C), nitrogen (N), and phosphorus (P) in the foliar litter of Fargesia nitida and Salix paraplesia in response to gap locations was determined in an alpine forest of the eastern Qinghai-Tibet Plateau via a 2-year litter decomposition experiment. The daily release rates of C, N, and P increased from the closed canopy to the gap centers during the two winters, the two later growing seasons and the entire 2 years, whereas this trend was reversed during the two early growing seasons. The pairwise ratios among C, N, and P converged as the litter decomposition proceeded. Compared with the closed canopy, the gap centers displayed higher C:P and N:P ratio but a lower C:N ratio as the decomposition proceeded. Alpine forest gaps accelerate the release of C, N, and P in decomposing shrub litter, implying that reduced snow cover resulting from vanishing gaps may inhibit the release of these elements in alpine forests.

  2. Carbon-nitrogen interactions and biomass partitioning of Carex rostrata grown at three levels of nitrogen supply

    Energy Technology Data Exchange (ETDEWEB)

    Saarinen, T. [Helsinki Univ. (Finland). Dept. of Ecology and Systematics

    1996-12-31

    Biomass and production of vascular plants constitutes a major source of carbon input in peatlands. As rates of decomposition vary considerably with depth, the vertical distribution of biomass may substantially affect accumulation of carbon in peatlands. Therefore, allocation patterns between shoot and roots are particularly important when considering carbon balance of peatland ecosystems. The stimulatory effect of increasing atmospheric concentration of CO{sub 2} or photosynthesis may increase availability of carbon to most C3 plants. Availability of nitrogen may also alter both due to increased atmospheric deposition and changer in mineralisation rates associated with climate change. Most root-shoot partitioning models predict that allocation of biomass is dependent of the availability and uptake of carbon and nitrogen. A decrease in supply of carbon would favour allocation to shoots and a decrease in supply of nitrogen would increase allocation to roots. At a cellular level, non structural carbohydrates and free amino acids are thought to represent the biochemically available fraction of carbon and nitrogen, respectively. The aim of this work is study the long-term growth responses of Carex rostrata to changes in the availability of nitrogen. Special attention is paid to soluble sugars ant free amino acids, which may control partitioning of biomass. (10 refs.)

  3. Carbon and nitrogen dynamics in early stages of forest litter decomposition as affected by nitrogen addition

    Institute of Scientific and Technical Information of China (English)

    DENG Xiao-wen; LIU Ying; HAN Shi-jie

    2009-01-01

    The effects of nitrogen (N) availability and tree species on the dynamics of carbon and nitrogen at early stage of decomposition of forest litter were studied in a 13-week laboratory incubation experiment. Fresh litter samples including needle litter (Pinus koraiensis) and two types of broadleaf litters (Quercus mongolica and Tilia amurensis) were collected from a broadleaf-korean pine mixed forest in the northern slope of Changbai Mountain (China). Different doses of N (equal to 0, 30 and 50 kg·ha-1yr-1, respectively, as NH4NO3) were added to litter during the experiment period. The litter decomposition rate expressed as mass loss and respiration rate increased significantly with increasing N availability. The mass loss and cumulative CO2-C emission were higher in leaf litter compared to that in needle litter. The dissolved organic Carbon (DOC) concentrations in litter leachate varied widely between the species, but were not greatly affected by N treatments. Regardless of the N addition rate, both N treatments and species had no significant effect on dissolved organic N (DON) concentrations in litter leachate. About 52·78% of added N was retained in the litter. The percentage of N retention was positively correlated (R2=0.91, p<0.05) with the litter mass loss. This suggested that a forest floor with easily decomposed litter might have higher potential N sink strength than that with more slowly decomposed litter.

  4. Soil Carbon and Nitrogen Stocks of Different Hawaiian Sugarcane Cultivars

    Directory of Open Access Journals (Sweden)

    Rebecca Tirado-Corbalá

    2015-06-01

    Full Text Available Sugarcane has been widely used as a biofuel crop due to its high biological productivity, ease of conversion to ethanol, and its relatively high potential for greenhouse gas reduction and lower environmental impacts relative to other derived biofuels from traditional agronomic crops. In this investigation, we studied four sugarcane cultivars (H-65-7052, H-78-3567, H-86-3792 and H-87-4319 grown on a Hawaiian commercial sugarcane plantation to determine their ability to store and accumulate soil carbon (C and nitrogen (N across a 24-month growth cycle on contrasting soil types. The main study objective establish baseline parameters for biofuel production life cycle analyses; sub-objectives included (1 determining which of four main sugarcane cultivars sequestered the most soil C and (2 assessing how soil C sequestration varies among two common Hawaiian soil series (Pulehu-sandy clay loam and Molokai-clay. Soil samples were collected at 20 cm increments to depths of up to 120 cm using hand augers at the three main growth stages (tillering, grand growth, and maturity from two experimental plots at to observe total carbon (TC, total nitrogen (TN, dissolved organic carbon (DOC and nitrates (NO−3 using laboratory flash combustion for TC and TN and solution filtering and analysis for DOC and NO−3. Aboveground plant biomass was collected and subsampled to determine lignin and C and N content. This study determined that there was an increase of TC with the advancement of growing stages in the studied four sugarcane cultivars at both soil types (increase in TC of 15–35 kg·m2. Nitrogen accumulation was more variable, and NO−3 (<5 ppm were insignificant. The C and N accumulation varies in the whole profile based on the ability of the sugarcane cultivar’s roots to explore and grow in the different soil types. For the purpose of storing C in the soil, cultivar H-65-7052 (TC accumulation of ~30 kg·m−2 and H-86-3792 (25 kg·m−2 rather H-78

  5. Synthesis of polybenzoxazine based nitrogen-rich porous carbons for carbon dioxide capture

    Science.gov (United States)

    Wan, Liu; Wang, Jianlong; Feng, Chong; Sun, Yahui; Li, Kaixi

    2015-04-01

    Nitrogen-rich porous carbons (NPCs) were synthesized from 1,5-dihydroxynaphthalene, urea, and formaldehyde based on benzoxazine chemistry by a soft-templating method with KOH chemical activation. They possess high surface areas of 856.8-1257.8 m2 g-1, a large pore volume of 0.15-0.65 cm3 g-1, tunable pore structure, high nitrogen content (5.21-5.32 wt%), and high char yields. The amount of the soft-templating agent F127 has multiple influences on the textural and chemical properties of the carbons, affecting the surface area and pore structure, impacting the compositions of nitrogen species and resulting in an improvement of the CO2 capture performance. At 1 bar, high CO2 uptake of 4.02 and 6.35 mmol g-1 at 25 and 0 °C was achieved for the sample NPC-2 with a molar ratio of F127 : urea = 0.010 : 1. This can be attributed to its well-developed micropore structure and abundant pyridinic nitrogen, pyrrolic nitrogen and pyridonic nitrogen functionalities. The sample NPC-2 also exhibits a remarkable selectivity for CO2/N2 separation and a fast adsorption/desorption rate and can be easily regenerated. This suggests that the polybenzoxazine-based NPCs are desirable for CO2 capture because of possessing a high micropore surface area, a large micropore volume, appropriate pore size distribution, and a large number of basic nitrogen functionalities.Nitrogen-rich porous carbons (NPCs) were synthesized from 1,5-dihydroxynaphthalene, urea, and formaldehyde based on benzoxazine chemistry by a soft-templating method with KOH chemical activation. They possess high surface areas of 856.8-1257.8 m2 g-1, a large pore volume of 0.15-0.65 cm3 g-1, tunable pore structure, high nitrogen content (5.21-5.32 wt%), and high char yields. The amount of the soft-templating agent F127 has multiple influences on the textural and chemical properties of the carbons, affecting the surface area and pore structure, impacting the compositions of nitrogen species and resulting in an improvement of the

  6. Studies on organic carbon, nitrogen and phosphorous in the sediments of Mandovi Estuary, Goa

    Digital Repository Service at National Institute of Oceanography (India)

    Nasnolkar, C.M.; Shirodkar, P.V.; Singbal, S.Y.S.

    Sediment organic carbon, total nitrogen, total phosphorous and hydrography of the overlying waters of the estuarine region in Mandovi Estuary, Goa, India have been studied. The relationship of carbon and nutrients with sediment characteristics...

  7. Fluorescently tuned nitrogen-doped carbon dots from carbon source with different content of carboxyl groups

    Directory of Open Access Journals (Sweden)

    Hao Wang

    2015-08-01

    Full Text Available In this study, fluorescent nitrogen-doped carbon dots (NCDs were tuned via varying the sources with different number of carboxyl groups. Owing to the interaction between amino and carboxyl, more amino groups conjugate the surface of the NCDs by the source with more carboxyl groups. Fluorescent NCDs were tuned via varying the sources with different content of carboxyl groups. Correspondingly, the nitrogen content, fluorescence quantum yields and lifetime of NCDs increases with the content of carboxyl groups from the source. Furthermore, cytotoxicity assay and cell imaging test indicate that the resultant NCDs possess low cytotoxicity and excellent biocompatibility.

  8. Fluorescently tuned nitrogen-doped carbon dots from carbon source with different content of carboxyl groups

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hao; Wang, Yun; Dai, Xiao; Zou, Guifu, E-mail: kqzhang@suda.edu.cn, E-mail: zouguifu@suda.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Gao, Peng; Zhang, Ke-Qin, E-mail: kqzhang@suda.edu.cn, E-mail: zouguifu@suda.edu.cn; Du, Dezhuang [National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou 215123 (China); Guo, Jun [Testing and Analysis Center, Soochow University, Suzhou 215123 (China)

    2015-08-01

    In this study, fluorescent nitrogen-doped carbon dots (NCDs) were tuned via varying the sources with different number of carboxyl groups. Owing to the interaction between amino and carboxyl, more amino groups conjugate the surface of the NCDs by the source with more carboxyl groups. Fluorescent NCDs were tuned via varying the sources with different content of carboxyl groups. Correspondingly, the nitrogen content, fluorescence quantum yields and lifetime of NCDs increases with the content of carboxyl groups from the source. Furthermore, cytotoxicity assay and cell imaging test indicate that the resultant NCDs possess low cytotoxicity and excellent biocompatibility.

  9. Leaf and canopy conductance in aspen and aspen-birch forests under free-air enrichment of carbon dioxide and ozone.

    Science.gov (United States)

    Uddling, Johan; Teclaw, Ronald M; Pregitzer, Kurt S; Ellsworth, David S

    2009-11-01

    Increasing concentrations of atmospheric carbon dioxide (CO2) and tropospheric ozone (O3) have the potential to affect tree physiology and structure, and hence forest feedbacks on climate. Here, we investigated how elevated concentrations of CO2 (+45%) and O3 (+35%), alone and in combination, affected conductance for mass transfer at the leaf and canopy levels in pure aspen (Populus tremuloides Michx.) and in mixed aspen and birch (Betula papyrifera Marsh.) forests in the free-air CO2-O3 enrichment experiment near Rhinelander, Wisconsin (Aspen FACE). The study was conducted during two growing seasons, when steady-state leaf area index (L) had been reached after > 6 years of exposure to CO2- and O3-enrichment treatments. Canopy conductance (g(c)) was estimated from stand sap flux, while leaf-level conductance of sun leaves in the upper canopy was derived by three different and independent methods: sap flux and L in combination with vertical canopy modelling, leaf 13C discrimination methodology in combination with photosynthesis modelling and leaf-level gas exchange. Regardless of the method used, the mean values of leaf-level conductance were higher in trees growing under elevated CO2 and/or O3 than in trees growing in control plots, causing a CO2 x O3 interaction that was statistically significant (P aspen and mixed aspen-birch communities. These results demonstrate that short-term primary stomatal closure responses to elevated CO2 and O3 were completely offset by long-term cumulative effects of these trace gases on tree and stand structure in determining canopy- and leaf-level conductance in pure aspen and mixed aspen-birch forests. Our results, together with the findings from other long-term FACE experiments with trees, suggest that model assumptions of large reductions in stomatal conductance under rising atmospheric CO2 are very uncertain for forests.

  10. Soil nitrogen and carbon impacts of raising chickens on pasture

    Science.gov (United States)

    Ryals, R.; Leach, A.; Tang, J.; Hastings, M. G.; Galloway, J. N.

    2014-12-01

    Chicken is the most consumed meat in the US, and production continues to intensify rapidly around the world. Chicken manure from confined feeding operations is typically applied in its raw form to nearby croplands, resulting in hotspots of soil nitrous oxide (N2O) emissions. Pasture-raised chicken is an alternative to industrial production and is growing in popularity with rising consumer demand for more humanely raised protein sources. In this agricultural model, manure is deposited directly onto grassland soils where it is thought to increase pools of soil carbon and nitrogen. The fate of manure nitrogen from pasture-raised chicken production remains poorly understood. We conducted a controlled, replicated experiment on a permaculture farm in Charlottesville, Virginia (Timbercreek Organics) in which small chicken coops (10 ft x 12 ft) were moved daily in a pasture. We measured manure deposition rates, soil inorganic nitrogen pools, soil moisture, and soil N2O and CO2 emissions. Measurements were made for the 28-day pasture life of three separate flocks of chickens in the spring, summer, and fall. Each flock consisted of approximately 200-300 chickens occupying three to five coops (~65 chickens/coop). Measurements were also made in paired ungrazed control plots. Manure deposition rates were similar across flocks and averaged 1.5 kgdrywt ha-1 during the spring grazing event and 4.0 kgdrywt ha-1 during the summer and fall grazing events. Manure deposition was relatively constant over the four weeks pasture-lifetime of the chickens. Compared to control plots, grazed areas exhibited higher soil N2O and CO2 fluxes. The magnitude of these fluxes diminished significantly over the four-week span. Soil gas fluxes significantly increased following rainfall events. For a given rainfall event, higher fluxes were observed from transects that were grazed more recently. Soil gaseous reactive nitrogen losses were less in this pasture system compared to cultivated field amended

  11. Short and long-term impacts of nitrogen deposition on carbon sequestration by forest ecosystems

    NARCIS (Netherlands)

    Vries, de W.; Du, E.; Butterbach-Bahl, K.

    2014-01-01

    The carbon to nitrogen response of forest ecosystems depends on the possible occurrence of nitrogen limitation versus possible co-limitations by other drivers, such as low temperature or availability of phosphorus. A combination of nitrogen retention estimates and stoichiometric scaling is used to i

  12. Controllable-nitrogen doped carbon layer surrounding carbon nanotubes as novel carbon support for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, P.L.; Hsu, C.H.; Wu, H.M.; Hsu, W.S. [Department of Chemical Engineering, National Cheng Kung University, Tainan (China); Kuo, D. [Department of Biochemistry, University of Washington, Seattle, WA (United States)

    2012-08-15

    Novel nitrogen-doped carbon layer surrounding carbon nanotubes composite (NC-CNT) (N/C ratio 3.3-14.3 wt.%) as catalyst support has been prepared using aniline as a dispersant to carbon nanotubes (CNTs) and as a source for both carbon and nitrogen coated on the surface of the CNTs, where the amount of doped nitrogen is controllable. The NC-CNT so obtained were characterized with scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption and desorption isotherms. A uniform dispersion of Pt nanoparticles (ca. 1.5-2.0 nm) was then anchored on the surface of NC-CNT by using aromatic amine as a stabilizer. For these Pt/NC-CNTs, cyclic voltammogram measurements show a high electrochemical activity surface area (up to 103.7 m{sup 2} g{sup -1}) compared to the commercial E-TEK catalyst (55.3 m{sup 2} g{sup -1}). In single cell test, Pt/NC-CNT catalyst has greatly enhanced catalytic activity toward the oxygen reduction reaction, resulting in an enhancement of ca. 37% in mass activity compared with that of E-TEK. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Current-voltage characteristics of carbon nanotubes with substitutional nitrogen

    DEFF Research Database (Denmark)

    Kaun, C.C.; Larade, B.; Mehrez, H.;

    2002-01-01

    We report ab initio analysis of current-voltage (I-V) characteristics of carbon nanotubes with nitrogen substitution doping. For zigzag semiconducting tubes, doping with a single N impurity increases current flow and, for small radii tubes, narrows the current gap. Doping a N impurity per nanotube...... unit cell generates a metallic transport behavior. Nonlinear I-V characteristics set in at high bias and a negative differential resistance region is observed for the doped tubes. These behaviors can be well understood from the alignment/mis-alignment of the current carrying bands in the nanotube leads...... due to the applied bias voltage. For a armchair metallic nanotube, a reduction of current is observed with substitutional doping due to elastic backscattering by the impurity....

  14. Nitrogen Deposition Effects on Soil Carbon Dynamics in Temperate Forests

    DEFF Research Database (Denmark)

    Ginzburg Ozeri, Shimon

    Soils contain the largest fraction of terrestrial carbon (C). Understanding the factors regulating the decomposition and storage of soil organic matter (SOM) is essential for predictions of the C sink strength of the terrestrial environment in the light of global change. Elevated long-term nitrogen...... (N) deposition into forest ecosystems has been increasing globally and was hypothesized to raise soil organic C (SOC) stocks by increasing forest productivity and by reducing SOM decomposition. Yet, these effects of N deposition on forest SOC stocks are uncertain and largely based on observations...... edges were used to study the effects of varying N deposition load on SOC stocks and fluxes as well as on the temperature sensitivity of SOM respiration. In a third study, the effects of 20 years of continuous experimental N addition (35 kg N ha-1 year-1) on soil C budget were investigated. Our general...

  15. Low Carbon Costs of Nitrogen Fixation in Tropical Dry Forests

    Science.gov (United States)

    Gei, M. G.; Powers, J. S.

    2015-12-01

    Legume tree species with the ability to fix nitrogen (N) are highly diverse and widespread across tropical forests but in particular in the dry tropics. Their ecological success in lower latitudes has been called a "paradox": soil N in the tropics is thought to be high, while acquiring N through fixation incurs high energetic costs. However, the long held assumptions that N fixation is limited by photosynthate and that N fixation penalizes plant productivity have rarely been tested, particularly in legume tree species. We show results from three different experiments where we grew eleven species of tropical dry forest legumes. We quantified plant biomass and N fixation using nodulation and the 15N natural isotope abundance (Ndfa or nitrogen derived from fixation). These data show little evidence for costs of N fixation in seedlings grown under different soil fertility, light regimes, and with different microbial communities. Seedling productivity did not incur major costs because of N fixation: indeed, the average slope between Ndfa and biomass was positive (range in slopes: -0.03 to 0.3). Moreover, foliar N, which varied among species, was tightly constrained and not correlated with Ndfa. This finding implies that legume species have a target N that does not change depending on N acquisition strategies. The process of N fixation in tropical legumes may be more carbon efficient than previously thought. This view is more consistent with the hyperabundance of members of this family in tropical ecosystems.

  16. Cellular Composition Changes and Nitrogen Uptake under Extra-Limited Nitrogen Conditions by Thermosynechococcus sp. CL-1 Carbon Biofixation

    Directory of Open Access Journals (Sweden)

    Tseng Chi-Ming

    2016-01-01

    Full Text Available Two types of culture systems were used (continuous and batch which were fed using a simulated absorbent from a scrubber with carbonate/bicarbonate as the carbon source and nitrate as the nitrogen source by a thermophile strain, Thermosynechococcus sp. CL-1 (TCL-1 at 50°C. The lipid, carbohydrate, and protein cellular components which can be used as bioenergy precursors along with their content as a function of various C/N ratios are quantified. Maximum lipid productivity of about 150 mg L−1 d−1 is obtained while the CO2 uptake rate is 917 mg L−1 d−1 at a dilution rate of 0.06 h−1 when both carbon and nitrogen sources are not limited. With high range of nitrogen concentrations batch culture test, TCL-1 reveals extra-high affinity on nitrogen source under limited carbon source conditions since the affinity constant is 0.12 mM. In addition, the flow of carbon fixed during photosynthesis seems to switch from the protein synthesis pathway to forming carbohydrate rather than lipid under N-limitation and a high C/N ratio for TCL-1, resulting in a maximal carbohydrate content of 61%. Consequently, TCL-1 is an appropriate candidate to treat the wastewater of environment and produce the bioenergy precursors under extreme limited nitrogen conditions.

  17. Particulate organic carbon and nitrogen export from major Arctic rivers

    Science.gov (United States)

    McClelland, J. W.; Holmes, R. M.; Peterson, B. J.; Raymond, P. A.; Striegl, R. G.; Zhulidov, A. V.; Zimov, S. A.; Zimov, N.; Tank, S. E.; Spencer, R. G. M.; Staples, R.; Gurtovaya, T. Y.; Griffin, C. G.

    2016-05-01

    Northern rivers connect a land area of approximately 20.5 million km2 to the Arctic Ocean and surrounding seas. These rivers account for ~10% of global river discharge and transport massive quantities of dissolved and particulate materials that reflect watershed sources and impact biogeochemical cycling in the ocean. In this paper, multiyear data sets from a coordinated sampling program are used to characterize particulate organic carbon (POC) and particulate nitrogen (PN) export from the six largest rivers within the pan-Arctic watershed (Yenisey, Lena, Ob', Mackenzie, Yukon, Kolyma). Together, these rivers export an average of 3055 × 109 g of POC and 368 × 109 g of PN each year. Scaled up to the pan-Arctic watershed as a whole, fluvial export estimates increase to 5767 × 109 g and 695 × 109 g of POC and PN per year, respectively. POC export is substantially lower than dissolved organic carbon export by these rivers, whereas PN export is roughly equal to dissolved nitrogen export. Seasonal patterns in concentrations and source/composition indicators (C:N, δ13C, Δ14C, δ15N) are broadly similar among rivers, but distinct regional differences are also evident. For example, average radiocarbon ages of POC range from ~2000 (Ob') to ~5500 (Mackenzie) years before present. Rapid changes within the Arctic system as a consequence of global warming make it challenging to establish a contemporary baseline of fluvial export, but the results presented in this paper capture variability and quantify average conditions for nearly a decade at the beginning of the 21st century.

  18. Tillage and manure effects on soil and aggregate-associated carbon and nitrogen

    OpenAIRE

    Mikha, M.M.; C. W. Rice

    2004-01-01

    Metadata only record This study assesses the impacts of tillage methods (conventional(CT) versus no-tillage(NT)) and nitrogen source (fertilizer(F) versus manure(M)) on soil aggregate size and the associated soil carbon and nitrogen. They find that both no-tillage and manure increase soil aggregate size, with the combination of the two producing the greatest soil aggregation. Likewise, there was greater total carbon and nitrogen in the soil for the no-tillage and manure treatments.

  19. Synthesis and characterization of well-aligned carbon nitrogen nanotubes by microwave plasma chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    马旭村; 徐贵昌; 王恩哥

    2000-01-01

    Well-aligned carbon nitrogen nanotube films have been synthesized successfully on meso-porous silica substrates by microwave plasma chemical vapor deposition (MWPCVD) method. Studies on their morphology, structure, and composition by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX), respectively, indicate that these nanotubes consist of linearly polymerized carbon nitrogen nanobells, and the nitrogen atoms have been doped into carbon netweork to form a new structure C1-xNx( x = 0.16±0.01). X-ray photoelectron spectroscopy (XPS) results of the samples further demonstrate that carbon bonds cova-lently with nitrogen in all the carbon nitrogen nanotube films.

  20. Soil Inorganic Nitrogen and Microbial biomass Carbon and Nitrogen Under Pine Plantations in Zhanggutai Sandy Soil

    Institute of Scientific and Technical Information of China (English)

    YU Zhan-Yuan; CHEN Fu-Sheng; ZENG De-Hui; ZHAO Qiong; CHEN Guang-Sheng

    2008-01-01

    The dynamics of soil inorganic nitrogen (NH+4-N and NO-3N) and microbial biomass carbon (Cmic) and nitrogen (Nmic) under 30-year-old fenced Pinus sylvestris L. var. mongolica Litvin (SF), unfenced P. sylvestris L. var. mongolica Litvin (SUF), and unfenced Pinus densiflora Siebold et Zucc. (DUF) plantations in the Zhanggutai sandy soil of China were studied during Apr. to Oct. 2004 by the in situ closed-top core incubation method. All mentioned C and N indices in each stand type fluctuated over time. The ranges of inorganic N, Cmic, and Nmic contents in the three stand types were 0.7-2.6, 40.0-128.9, and 5.4-15.2 μg g-1, respectively. The average contents of soil NH+4-N and Cmic under the three 30-year-old pine plantations were not different. However, soil NO-3-N and total inorganic N contents decreased in the order of SUF > SF > DUF, the Nmic content was in the order of SF = SUF > DUF, and the Cmic:Nmic ratio was in the order of SUF = DUF > SF. Seasonal variations were observed in soil inorganic N, microbial biomass, and plant growth. These seasonal variations had certain correlations with microbe and plant N use in the soil, and their competition for NH+4-N was mostly regulated by soil N availability. The influence of tree species on inorganic N and Nmic were mainly because of differences in litter quality. Lack of grazing decreased the Cmic:N ratio owing to decreased carbon output and increased the ability of soil to supply N. The soil N supply under the P. sylvestris var. mongolica plantation was lower than under the P. densiflora plantation.

  1. Nitrogen removal efficiency of iron-carbon micro-electrolysis system treating high nitrate nitrogen organic pharmaceutical wastewater

    Institute of Scientific and Technical Information of China (English)

    周健; 段送华; 陈垚; 胡斌

    2009-01-01

    The nitrate nitrogen removal efficiency of iron-carbon micro-electrolysis system was discussed in treating pharmaceutical wastewater with high nitrogen and refractory organic concentration. The results show that the granularity of fillings,pH,volume ratios of iron-carbon and gas-water,and HRT. have significant effects on the nitrogen removal efficiency of iron-carbon micro-electrolysis system. The iron-carbon micro-electrolysis system has a good removal efficiency of pharmaceutical wastewater with high nitrogen and refractory organic concentration when the influent TN,NH4+-N,NO3--N and BOD5/CODCr are 823 mg/L,30 mg/L,793 mg/L and 0.1,respectively,at the granularity of iron and carbon 0.425 mm,pH 3,iron-carbon ratio 3,gas-water ratio 5,HRT 1.5 h,and the removal rates of TN,NH4+-N and NO3--N achieve 51.5%,70% and 50.94%,respectively.

  2. Nitrogen-doped mesoporous carbons for high performance supercapacitors

    Science.gov (United States)

    Wu, Kai; Liu, Qiming

    2016-08-01

    The mesoporous carbons have been synthesized by using α-D(+)-Glucose, D-Glucosamine hydrochloride or their mixture as carbon precursors and mesoporous silicas (SBA-15 or MCF) as hard templates. The as-prepared products show a large pore volume (0.59-0.97 cm3 g-1), high surface areas (352.72-1152.67 m2 g-1) and rational nitrogen content (ca. 2.5-3.9 wt.%). The results of electrochemical tests demonstrate that both heteroatom doping and suitable pore structure play a decisive role in the performance of supercapacitors. The representative sample of SBA-15 replica obtained using D-Glucosamine hydrochloride only exhibits high specific capacitance (212.8 F g-1 at 0.5 A g-1) and good cycle durability (86.1% of the initial capacitance after 2000 cycles) in 6 M KOH aqueous electrolyte, which is attributed to the contribution of double layer capacitance and pseudo-capacitance. The excellent electrochemical performance makes it a promising electrode material for supercapacitors.

  3. Predicted phase diagram of boron-carbon-nitrogen

    Science.gov (United States)

    Zhang, Hantao; Yao, Sanxi; Widom, Michael

    2016-04-01

    Noting the structural relationships between phases of carbon and boron carbide with phases of boron nitride and boron subnitride, we investigate their mutual solubilities using a combination of first-principles total energies supplemented with statistical mechanics to address finite temperatures. Thus we predict the solid-state phase diagram of boron-carbon-nitrogen (B-C-N). Owing to the large energy costs of substitution, we find that the mutual solubilities of the ultrahard materials diamond and cubic boron nitride are negligible, and the same for the quasi-two-dimensional materials graphite and hexagonal boron nitride. In contrast, we find a continuous range of solubility connecting boron carbide to boron subnitride at elevated temperatures. An electron-precise ternary compound B13CN consisting of B12 icosahedra with NBC chains is found to be stable at all temperatures up to melting. It exhibits an order-disorder transition in the orientation of NBC chains at approximately T =500 K. We also propose that the recently discovered binary B13N2 actually has composition B12.67N2 .

  4. Nitrogen-Doped Carbon Dots for "green" Quantum Dot Solar Cells.

    Science.gov (United States)

    Wang, Hao; Sun, Pengfei; Cong, Shan; Wu, Jiang; Gao, Lijun; Wang, Yun; Dai, Xiao; Yi, Qinghua; Zou, Guifu

    2016-12-01

    Considering the environment protection, "green" materials are increasingly explored for photovoltaics. Here, we developed a kind of quantum dots solar cell based on nitrogen-doped carbon dots. The nitrogen-doped carbon dots were prepared by direct pyrolysis of citric acid and ammonia. The nitrogen-doped carbon dots' excitonic absorption depends on the N-doping content in the carbon dots. The N-doping can be readily modified by the mass ratio of reactants. The constructed "green" nitrogen-doped carbon dots solar cell achieves the best power conversion efficiency of 0.79 % under AM 1.5 G one full sun illumination, which is the highest efficiency for carbon dot-based solar cells.

  5. Mechanisms controlling soil carbon sequestration under atmospheric nitrogen deposition

    Energy Technology Data Exchange (ETDEWEB)

    R.L. Sinsabaugh; D.R. Zak; D.L. Moorhead

    2008-02-19

    Increased atmospheric nitrogen (N) deposition can alter the processing and storage of organic carbon in soils. In 2000, we began studying the effects of simulated atmospheric N deposition on soil carbon dynamics in three types of northern temperate forest that occur across a wide geographic range in the Upper Great Lakes region. These ecosystems range from 100% oak in the overstory (black oak-white oak ecosystem; BOWO) to 0% overstory oak (sugar maple-basswood; SMBW) and include the sugar maple-red oak ecosystem (SMRO) that has intermediate oak abundance. The leaf litter biochemistry of these ecosystems range from highly lignified litter (BOWO) to litter of low lignin content (SMBW). We selected three replicate stands of each ecosystem type and established three plots in each stand. Each plot was randomly assigned one of three levels of N deposition (0, 30 & 80 kg N ha-1 y-1) imposed by adding NaNO3 in six equal increments applied over the growing season. Through experiments ranging from the molecular to the ecosystem scales, we produced a conceptual framework that describes the biogeochemistry of soil carbon storage in N-saturated ecosystems as the product of interactions between the composition of plant litter, the composition of the soil microbial community and the expression of extracellular enzyme activities. A key finding is that atmospheric N deposition can increase or decrease the soil C storage by modifying the expression of extracellular enzymes by soil microbial communities. The critical interactions within this conceptual framework have been incorporated into a new class of simulations called guild decomposition models.

  6. Nitrogen management and the future of food: lessons from the management of energy and carbon.

    Science.gov (United States)

    Socolow, R H

    1999-05-25

    The food system dominates anthropogenic disruption of the nitrogen cycle by generating excess fixed nitrogen. Excess fixed nitrogen, in various guises, augments the greenhouse effect, diminishes stratospheric ozone, promotes smog, contaminates drinking water, acidifies rain, eutrophies bays and estuaries, and stresses ecosystems. Yet, to date, regulatory efforts to limit these disruptions largely ignore the food system. There are many parallels between food and energy. Food is to nitrogen as energy is to carbon. Nitrogen fertilizer is analogous to fossil fuel. Organic agriculture and agricultural biotechnology play roles analogous to renewable energy and nuclear power in political discourse. Nutrition research resembles energy end-use analysis. Meat is the electricity of food. As the agriculture and food system evolves to contain its impacts on the nitrogen cycle, several lessons can be extracted from energy and carbon: (i) set the goal of ecosystem stabilization; (ii) search the entire production and consumption system (grain, livestock, food distribution, and diet) for opportunities to improve efficiency; (iii) implement cap-and-trade systems for fixed nitrogen; (iv) expand research at the intersection of agriculture and ecology, and (v) focus on the food choices of the prosperous. There are important nitrogen-carbon links. The global increase in fixed nitrogen may be fertilizing the Earth, transferring significant amounts of carbon from the atmosphere to the biosphere, and mitigating global warming. A modern biofuels industry someday may produce biofuels from crop residues or dedicated energy crops, reducing the rate of fossil fuel use, while losses of nitrogen and other nutrients are minimized.

  7. Similar reproductive status and body size of horse flies (Diptera: Tabanidae) attracted to carbon dioxide-baited canopy traps and a Jersey bullock.

    Science.gov (United States)

    Leprince, D J; Hribar, L J; Foil, L D

    1992-11-01

    The reproductive status and body size of four Tabanus species collected from canopy traps baited with carbon dioxide and from a Jersey bullock were compared. Parity rates, sperm prevalence, stage of follicular development in terminal follicles of parous females, prevalence of females retaining eggs, average number of eggs retained in parous flies, and the body size of parous females did not differ significantly between sampling methods. Based on the presence of nulliparous host-seeking flies, Tabanus pallidescens Philip and T. wilsoni Pechuman can be added to the list of tabanids found to be anautogenous.

  8. Influence of carbon and nitrogen sources on growth, nitrogenase activity, and carbon metabolism of Gluconacetobacter diazotrophicus.

    Science.gov (United States)

    Tejera, Noel A; Ortega, Eduardo; Rodés, Rosa; Lluch, Carmen

    2004-09-01

    The effects of different carbon and nitrogen sources on the growth, nitrogenase activity, and carbon metabolism of Gluconacetobacter diazotrophicus were investigated. The amino acids asparagine, aspartic acid, and glutamic acid affected microbial growth and nitrogenase activity. Several enzymatic activities involved in the tricarboxylic acid cycle were affected by the carbon source used. In addition, glucose and gluconate significantly increased the oxygen consumption (respiration rate) of whole cells of G. diazotrophicus grown under aerobic conditions. Enzymes responsible for direct oxidation of glucose and gluconate were especially active in cells grown with sucrose and gluconate. The presence of amino acids in the apoplastic and symplastic sap of sugarcane stems suggests that these compounds might be of importance in the regulation of growth and nitrogenase activity during the symbiotic association. The information obtained from the plant-bacterium association together with the results of other biochemical studies could contribute to the development of biotechnological applications of G. diazotrophicus.

  9. Mechanochemical Synthesis of Visible-light Induced Photocatalyst with Nitrogen and Carbon Doping

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nitrogen and/or carbon doped titania photocatalysts were prepared by a novel mechanochemical method. The prepared powders possessed two absorption edges around 400 and 540 nm wavelengths and showed excellent photocatalytic ability for nitrogen monoxide oxidation under visible light irradiation. Under the irradiation of visible light of wavelength >510 nm, 37% of nitrogen monoxide could be continuously removed by the carbon and nitrogen co-doped titania prepared by planetary ball milling of P-25 titania-10% hexamethylenetetramine mixture followed by calcination in air at 400 ℃.

  10. Doping of carbon nanotubes with nitrogen improves protein coverage whilst retaining correct conformation

    Science.gov (United States)

    Burch, Hilary J.; Antoranz Contera, Sonia; de Planque, Maurits R. R.; Grobert, Nicole; Ryan, J. F.

    2008-09-01

    Relevant parameters for non-covalent protein functionalization of carbon nanotubes are explored. Multiwalled carbon nanotubes are carboxylated and functionalized with metalloproteins. Using atomic force microscopy (AFM) we quantitatively determine that coverage with nitrogen-doped multiwalled carbon nanotubes is superior compared to coverage with un-doped multiwalled carbon nanotubes, due to enhanced carboxylation. Conformational analysis using a combination of AFM, antibody binding assays, circular dichroism and UV-visible spectroscopy demonstrates that the metalloproteins retain their native structure when adsorbed to nitrogen-doped multiwalled carbon nanotubes irrespective of their size, charge or folding motif.

  11. Anatomical basis of the change in leaf mass per area and nitrogen investment with relative irradiance within the canopy of eight temperate tree species

    Science.gov (United States)

    Aranda, I.; Pardo, F.; Gil, L.; Pardos, J. A.

    2004-05-01

    Changes in leaf mass per area (LMA), nitrogen content on a mass-basis (N m) and on an area basis (N a) with relative irradiance were assessed in leaves of eight temperate species harvested at different depths in a canopy. Relative irradiance (GSF) at the points of leaf sampling was estimated by hemispheric photographs. There was a strong species-dependent positive relationship between LMA and GSF for all species. Shade-tolerant species such as Fagus sylvatica showed lower LMA for the same GSF than less tolerant species as Quercus pyrenaica or Quercus petraea. The only evergreen species in the study, Ilex aquifollium, had the highest LMA, independent of light environment, with minimum values much higher than the rest of the broad-leaved species studied. There was no relation between N m and GSF for most species studied and only a very weak relation for the relative shade-intolerant species Q. pyrenaica. Within each species, the pattern of N a investment with regard to GSF was linked mainly to LMA. At the same relative irradiance, differences in N a among species were conditioned both by the LMA-GSF relationship and by the species N m value. The lowest N m value was measured in I. aquifollium (14.3 ± 0.6 mg g -1); intermediate values in Crataegus monogyna (16.9 ± 0.6 mg g -1) and Prunus avium (19.1 ± 0.6 mg g -1) and higher values, all in a narrow range (21.3 ± 0.6 to 23 ± 0.6 mg g -1), were measured for the other five species. Changes in LMA with the relative irradiance were linked both to lamina thickness (LT) and to palisade/spongy parenchyma ratio (PP/SP). In the second case, the LMA changes may be related to an increase in lamina density as palisade parenchyma involves higher cell packing than spongy parenchyma. However, since PP/SP ratio showed a weak species-specific relationship with LMA, the increase in LT should be the main cause of LMA variation.

  12. A facile approach towards increasing the nitrogen-content in nitrogen-doped carbon nanotubes via halogenated catalysts

    Science.gov (United States)

    Ombaka, L. M.; Ndungu, P. G.; Omondi, B.; McGettrick, J. D.; Davies, M. L.; Nyamori, V. O.

    2016-03-01

    Nitrogen-doped carbon nanotubes (N-CNTs) have been synthesized at 850 °C via a CVD deposition technique by use of three ferrocenyl derivative catalysts, i.e. para-CN, -CF3 and -Cl substituted-phenyl rings. The synthesized catalysts have been characterized by NMR, IR, HR-MS and XRD. The XRD analysis of the para-CF3 catalyst indicates that steric factors influence the X-ray structure of 1,1‧-ferrocenylphenyldiacrylonitriles. Acetonitrile or pyridine was used as carbon and nitrogen sources to yield mixtures of N-CNTs and carbon spheres (CS). The N-CNTs obtained from the para-CF3 catalysts, in pyridine, have the highest nitrogen-doping level, show a helical morphology and are less thermally stable compared with those synthesized by use of the para-CN and -Cl as catalyst. This suggests that fluorine heteroatoms enhance nitrogen-doping in N-CNTs and formation of helical-N-CNTs (H-N-CNTs). The para-CF3 and para-Cl catalysts in acetonitrile yielded iron-filled N-CNTs, indicating that halogens promote encapsulation of iron into the cavity of N-CNT. The use of acetonitrile, as carbon and nitrogen source, with the para-CN and -Cl as catalysts also yielded a mixture of N-CNTs and carbon nanofibres (CNFs), with less abundance of CNFs in the products obtained using para-Cl catalysts. However, para-CF3 catalyst in acetonitrile gave N-CNTs as the only shaped carbon nanomaterials.

  13. Carbon and nitrogen cycling in intertidal sediments near Doel, Scheldt Estuary

    NARCIS (Netherlands)

    Middelburg, J.J.; Klaver, G.; Nieuwenhuize, J.; Vlug, T.

    1995-01-01

    Carbon and nitrogen cycling in intertidal mud flat sediments in the Scheldt Estuary was studied using measurements of carbon dioxide, methane and nitrous oxide emission rates and pore-water profiles of ΣCO2, ammonium and nitrate. A comparison between chamber measured carbon dioxide fluxes and those

  14. Identification of nitrogen dopants in single-walled carbon nanotubes by scanning tunneling microscopy.

    Science.gov (United States)

    Tison, Yann; Lin, Hong; Lagoute, Jérôme; Repain, Vincent; Chacon, Cyril; Girard, Yann; Rousset, Sylvie; Henrard, Luc; Zheng, Bing; Susi, Toma; Kauppinen, Esko I; Ducastelle, François; Loiseau, Annick

    2013-08-27

    Using scanning tunnelling microscopy and spectroscopy, we investigated the atomic and electronic structure of nitrogen-doped single walled carbon nanotubes synthesized by chemical vapor deposition. The insertion of nitrogen in the carbon lattice induces several types of point defects involving different atomic configurations. Spectroscopic measurements on semiconducting nanotubes reveal that these local structures can induce either extended shallow levels or more localized deep levels. In a metallic tube, a single doping site associated with a donor state was observed in the gap at an energy close to that of the first van Hove singularity. Density functional theory calculations reveal that this feature corresponds to a substitutional nitrogen atom in the carbon network.

  15. Adsorption of nitrogen and carbon monoxide on clinoptilolite: determination and prediction of pure and binary isotherms

    Energy Technology Data Exchange (ETDEWEB)

    Triebe, R.W.; Tezel, F.H. [University of Ottawa, Ottawa, ON (Canada). Department of Chemical Engineering

    1995-10-01

    The adsorption of carbon monoxide and nitrogen on clinoptilolite is studied to determine the natural zeolite`s potential for air purification. Pure and binary isotherms were determined for nitrogen and carbon monoxide on a natural Turkish clinoptilolite under near ambient conditions. Experimentally determined isotherms are compared to predictions based on various models from the literature. The Wilson form of the Vacancy Solution Theory is the only model that provides reasonable agreement with the binary isotherm. Clinoptilolite is concluded to be a promising sorbent for separation of carbon monoxide and nitrogen. 30 refs., 11 figs., 5 tabs.

  16. Long-term nitrogen addition decreases carbon leaching in nitrogen-rich forest ecosystems

    Directory of Open Access Journals (Sweden)

    X. Lu

    2013-01-01

    Full Text Available Dissolved organic carbon (DOC plays a critical role in the carbon (C cycle of forest soils, and has been recently connected with global increases in nitrogen (N deposition. Most studies on effects of elevated N deposition on DOC have been carried out in N-limited temperate regions, with far fewer data available from N-rich ecosystems, especially in the context of chronically elevated N deposition. Furthermore, mechanisms for excess N-induced changes of DOC dynamics have been suggested to be different between the two kinds of ecosystems, because of the different ecosystem N status. The purpose of this study was to experimentally examine how long-term N addition affects DOC dynamics below the primary rooting zones (the upper 20 cm soils in typically N-rich lowland tropical forests. We have a primary assumption that long-term continuous N addition minimally affects DOC concentrations and effluxes in N-rich tropical forests. Experimental N addition was administered at the following levels: 0, 50, 100 and 150 kg N ha−1 yr−1, respectively. Results showed that seven years of N addition significantly decreased DOC concentrations in soil solution, and chemo-physical controls (solution acidity change and soil sorption rather than biological controls may mainly account for the decreases, in contrast to other forests. We further found that N addition greatly decreased annual DOC effluxes from the primary rooting zone and increased water-extractable DOC in soils. Our results suggest that long-term N deposition could increase soil C sequestration in the upper soils by decreasing DOC efflux from that layer in N-rich ecosystems, a novel mechanism for continued accumulation of soil C in old-growth forests.

  17. Long-term nitrogen addition decreases carbon leaching in a nitrogen-rich forest ecosystem

    Directory of Open Access Journals (Sweden)

    X. Lu

    2013-06-01

    Full Text Available Dissolved organic carbon (DOC plays a critical role in the carbon (C cycle of forest soils, and has been recently connected with global increases in nitrogen (N deposition. Most studies on effects of elevated N deposition on DOC have been carried out in N-limited temperate regions, with far fewer data available from N-rich ecosystems, especially in the context of chronically elevated N deposition. Furthermore, mechanisms for excess N-induced changes of DOC dynamics have been suggested to be different between the two kinds of ecosystems, because of the different ecosystem N status. The purpose of this study was to experimentally examine how long-term N addition affects DOC dynamics below the primary rooting zones (the upper 20 cm soils in typically N-rich lowland tropical forests. We have a primary assumption that long-term continuous N addition minimally affects DOC concentrations and effluxes in N-rich tropical forests. Experimental N addition was administered at the following levels: 0, 50, 100 and 150 kg N ha−1 yr−1, respectively. Results showed that seven years of N addition significantly decreased DOC concentrations in soil solution, and chemo-physical controls (solution acidity change and soil sorption rather than biological controls may mainly account for the decreases, in contrast to other forests. We further found that N addition greatly decreased annual DOC effluxes from the primary rooting zone and increased water-extractable DOC in soils. Our results suggest that long-term N deposition could increase soil C sequestration in the upper soils by decreasing DOC efflux from that layer in N-rich ecosystems, a novel mechanism for continued accumulation of soil C in old-growth forests.

  18. Dependence of Photosynthetic Capacity, Photosynthetic Pigment Allocation, and Carbon Storage on Nitrogen Levels in Foliage of Aspen Stands

    Science.gov (United States)

    Middleton, Elizabeth M.; Sullivan, Joseph H.; Papagno, Andrea J.

    2000-01-01

    The role of foliar nitrogen (N) in the seasonal dynamics and vertical canopy distribution of photosynthetic pigments, photosynthetic capacity, and carbon (C) storage was investigated in boreal broadleaved species. The study was conducted at two different aged stands (60 y and 15 y) in 1994 and 1996 in Saskatchewan, Canada as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). Foliage in upper and lower strata was examined for aspen (Populus tremuloides Michx.) and its associated hazelnut shrub (Corylus americana Walt.). We determined that C accumulation, expressed as dry mass per unit leaf area (mg C cm (exp -2)), was linearly dependent on N content (approximately 0.3- 3.5 mg N cm (exp -2))(r (exp 2) = 0.93, n=383, P less than 0.001) when eleven foliage groups were defined according to species, site, and developmental stage. C assembly was greatest in the upper aspen strata of both sites (seasonal average, 40.1 plus or minus 0.6 mg C cm (exp -2)), intermediate in the lower aspen strata (32.7 plus or minus 0.6), and considerably lower, and similar, in the hazelnut shrub layers (23.7 plus or minus 0.6) and in expanding aspen leaves (23.8 plus or minus 0.5); the lowest C assembly per unit N occurred in the two youngest, emerging leaf groups (17.1 plus or minus 0.6). Other relationships among physiological and biochemical variables were typically non-linear and were confounded by inclusion of the three groups of young (i.e., emerging or expanding) leaves, unless these were separately identified. Net C uptake, measured as photosynthetic capacity (A (sub max), micromole CO2 m (exp -2) s (exp -1)), was greater in aspen throughout the season, and optimal in mid-summer at a C:N ratio of approximately 18 (approximately 2.3 %N). When young leaves were excluded and logarithms of both variables were used, A (sub max) was approximately linearly dependent on N (mg N cm (exp-2) (r (exp 2) = 0.85, n= 193, P less than 0.001), attributed to incorporation of N into photosynthetic

  19. Relationships between Canopy Temperature, Leaf Chlorophyll Content and Grain Yield in Wheat Genotypes under Different Nitrogen Levels and Post-Anthesis Heat Stress Conditions

    Directory of Open Access Journals (Sweden)

    a Modhej

    2012-02-01

    Full Text Available Abstract In order to study the canopy, spike and flag leaf temperature in wheat genotypes under optimum and post-anthesis heat stress conditions and canopy relationships with some morphological and physiological characters, two separate field experiments were conducted in delayed and optimum sowing dates in Ahvaz, Iran in 2007-2008. The experimental site had a moderate winter and dry, hot summer. Plants with delayed sowing date experienced heat stress post-anthesis. Each split-polt experiment had a randomized complete block design with three replicates. The N application rates were (50, 100, and 150 KgNha-1 assigned in the main-plots. Sub-plots consisted of six bread and durum wheat genotypes. Temperature of canopy, spikes and flag leaf were measured in two growth stages (anthesis and milk stage using a hand-held infrared thermometer. Results indicated that, organs temperature was affected by genotypeenvironment. Although, organs temperature increased as the N rate decreased, the effect of N treatments on organs temperature was not significant. In post-anthesis heat stress conditions, the genotypes that had higher flag leaf and canopy temperature due to higher growth stage duration (such as Star and D-84-5, lower ability in leaf rolling (such as Showa and D-84-5 and higher leaf width (such as Star and D-84-5, had higher chlorophyll reduction under post-anthesis heat stress conditions. Keywords: Wheat, Post-anthesis heat stress, Canopy temperature, Chlorophyll content

  20. Effects of nitrogen content on structure and electrical properties of nitrogen-doped fluorinated diamond-like carbon films

    Institute of Scientific and Technical Information of China (English)

    XIAO Jian-rong; LI Xin-hai; WANG Zhi-xing

    2009-01-01

    Nitrogen-doped fluorinated diamond-like carbon (FN-DLC) films were prepared on single crystal silicon substrate by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) under different deposited conditions with CF4,CH4 and nitrogen as source gases.The influence of nitrogen content on the structure and electrical properties of the films was studied.The films were investigated in terms of surface morphology,microstructure,chemical composition and electrical properties.Atomic force microscopy (AFM) results revealed that the surface morphology of the films became smooth due to doping nitrogen.Fourier transform infrared absorption spectrometry (FTIR) results showed that amouts of C=N and C≡N bonds increased gradually with increasing nitrogen partial pressure r (r=p(N_2)/p(N_2+CF_4+CH_4)).Gaussian fit results of C 1s and N 1s in X-ray photoelectron spectra (XPS) showed that the incorporation of nitrogen presented mainly in the forms of β-C_3N_4 and a-CN_x (x=1,2,3) in the films.The current-voltage (I-V) measurement results showed that the electrical conductivity of the films increased with increasing nitrogen content.

  1. A one-step carbonization route towards nitrogen-doped porous carbon hollow spheres with ultrahigh nitrogen content for CO 2 adsorption

    KAUST Repository

    Wang, Yu

    2015-01-01

    © The Royal Society of Chemistry 2015. Nitrogen doped porous carbon hollow spheres (N-PCHSs) with an ultrahigh nitrogen content of 15.9 wt% and a high surface area of 775 m2 g-1 were prepared using Melamine-formaldehyde nanospheres as hard templates and nitrogen sources. The N-PCHSs were completely characterized and were found to exhibit considerable CO2 adsorption performance (4.42 mmol g-1).

  2. Decomposition rates and carbon:nitrogen ratios for different litter types, 2015

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data table contains mean decomposition rates and mean carbon:nitrogen ratios for different litter types buried in 7 marshes during 2015. Note that C:N data are...

  3. Assessment of the dynamics in nitrogen and carbon sequestration of European forest soils

    NARCIS (Netherlands)

    Vries, de W.; Salm, van der C.; Reinds, G.J.; Dise, N.B.; Gundersen, P.; Erisman, J.W.; Posch, M.

    2003-01-01

    This report describes the major result of a research project that focused on the assessment of the dynamics in nitrogen and carbon sequestration of European forest soils by estimation of the: (i) retention or release of nitrogen species for selected Intensive Monitoring plots by comparing the input,

  4. Modeling the effects of organic nitrogen uptake by plants on the carbon cycling of boreal ecosystems

    Directory of Open Access Journals (Sweden)

    Q. Zhu

    2013-08-01

    Full Text Available Boreal forest and tundra are the major ecosystems in the northern high latitudes in which a large amount of carbon is stored. These ecosystems are nitrogen-limited due to slow mineralization rate of the soil organic nitrogen. Recently, abundant field studies have found that organic nitrogen is another important nitrogen supply for boreal ecosystems. In this study, we incorporated a mechanism that allowed boreal plants to uptake small molecular amino acids into a process-based biogeochemical model, the Terrestrial Ecosystem Model (TEM, to evaluate the impact of organic nitrogen uptake on ecosystem carbon cycling. The new version of the model was evaluated at both boreal forest and tundra sites. We found that the modeled organic nitrogen uptake accounted for 36–87% of total nitrogen uptake by plants in tundra ecosystems and 26–50% for boreal forests, suggesting that tundra ecosystem might have more relied on the organic form of nitrogen than boreal forests. The simulated monthly gross ecosystem production (GPP and net ecosystem production (NEP tended to be larger with the new version of the model since the plant uptake of organic nitrogen alleviated the soil nitrogen limitation especially during the growing season. The sensitivity study indicated that the most important factors controlling the plant uptake of organic nitrogen were the maximum root uptake rate (Imax and the radius of the root (r0 in our model. The model uncertainty due to uncertain parameters associated with organic nitrogen uptake at tundra ecosystem was larger than at boreal forest ecosystems. This study suggests that considering the organic nitrogen uptake by plants is important to boreal ecosystem carbon modeling.

  5. Electrochemical Performance of Highly Mesoporous Nitrogen Doped Carbon Cathode in Lithium-Oxygen Batteries (Postprint)

    Science.gov (United States)

    2011-03-01

    Chem. Lett. 1 (2010) 2193–2203. [3] F.T. Wagner, B. Lakshmanan, M.F. Mathias, J. Phys. Chem. Lett. 1 (2010) 2204–2219. [4] D. Linden (Ed.), Handbook ...AFRL-RQ-WP-TP-2015-0052 ELECTROCHEMICAL PERFORMANCE OF HIGHLY MESOPOROUS NITROGEN DOPED CARBON CATHODE IN LITHIUM-OXYGEN BATTERIES ...01 March 2011 4. TITLE AND SUBTITLE ELECTROCHEMICAL PERFORMANCE OF HIGHLY MESOPOROUS NITROGEN DOPED CARBON CATHODE IN LITHIUM-OXYGEN BATTERIES

  6. Nitrogen-doped porous carbon monoliths from polyacrylonitrile (PAN) and carbon nanotubes as electrodes for supercapacitors

    Science.gov (United States)

    Wang, Yanqing; Fugetsu, Bunshi; Wang, Zhipeng; Gong, Wei; Sakata, Ichiro; Morimoto, Shingo; Hashimoto, Yoshio; Endo, Morinobu; Dresselhaus, Mildred; Terrones, Mauricio

    2017-01-01

    Nitrogen-doped porous activated carbon monoliths (NDP-ACMs) have long been the most desirable materials for supercapacitors. Unique to the conventional template based Lewis acid/base activation methods, herein, we report on a simple yet practicable novel approach to production of the three-dimensional NDP-ACMs (3D-NDP-ACMs). Polyacrylonitrile (PAN) contained carbon nanotubes (CNTs), being pre-dispersed into a tubular level of dispersions, were used as the starting material and the 3D-NDP-ACMs were obtained via a template-free process. First, a continuous mesoporous PAN/CNT based 3D monolith was established by using a template-free temperature-induced phase separation (TTPS). Second, a nitrogen-doped 3D-ACM with a surface area of 613.8 m2/g and a pore volume 0.366 cm3/g was obtained. A typical supercapacitor with our 3D-NDP-ACMs as the functioning electrodes gave a specific capacitance stabilized at 216 F/g even after 3000 cycles, demonstrating the advantageous performance of the PAN/CNT based 3D-NDP-ACMs. PMID:28074847

  7. Nitrogen-doped porous carbon monoliths from polyacrylonitrile (PAN) and carbon nanotubes as electrodes for supercapacitors

    Science.gov (United States)

    Wang, Yanqing; Fugetsu, Bunshi; Wang, Zhipeng; Gong, Wei; Sakata, Ichiro; Morimoto, Shingo; Hashimoto, Yoshio; Endo, Morinobu; Dresselhaus, Mildred; Terrones, Mauricio

    2017-01-01

    Nitrogen-doped porous activated carbon monoliths (NDP-ACMs) have long been the most desirable materials for supercapacitors. Unique to the conventional template based Lewis acid/base activation methods, herein, we report on a simple yet practicable novel approach to production of the three-dimensional NDP-ACMs (3D-NDP-ACMs). Polyacrylonitrile (PAN) contained carbon nanotubes (CNTs), being pre-dispersed into a tubular level of dispersions, were used as the starting material and the 3D-NDP-ACMs were obtained via a template-free process. First, a continuous mesoporous PAN/CNT based 3D monolith was established by using a template-free temperature-induced phase separation (TTPS). Second, a nitrogen-doped 3D-ACM with a surface area of 613.8 m2/g and a pore volume 0.366 cm3/g was obtained. A typical supercapacitor with our 3D-NDP-ACMs as the functioning electrodes gave a specific capacitance stabilized at 216 F/g even after 3000 cycles, demonstrating the advantageous performance of the PAN/CNT based 3D-NDP-ACMs.

  8. Effect of reaction temperature on structure and fluorescence properties of nitrogen-doped carbon dots

    Science.gov (United States)

    Zhang, Yi; Wang, Yaling; Feng, Xiaoting; Zhang, Feng; Yang, Yongzhen; Liu, Xuguang

    2016-11-01

    To investigate the effect of reaction temperature and nitrogen doping on the structure and fluorescence properties of carbon dots (CDs), six kinds of nitrogen-doped CDs (NCDs) were synthesized at reaction temperatures of 120, 140, 160, 180, 200 and 220 °C, separately, by using citric acid as carbon source and ammonia solution as nitrogen source. Nitrogen-free CDs (N-free CDs-180) was also prepared at 180 °C by using citric acid as the only carbon source for comparison. Results show that reaction temperature has obvious effect on carbonization degree, quantum yield (QY), ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) spectra but less effect on functional groups, nitrogen doping degree and fluorescence lifetime of NCDs. Compared with N-free CDs-180, NCDs-180 possesses enchanced QY and longer fluorescence lifetime. Doping nitrogen has obvious effect on UV-vis absorption and PL spectra but less effect on particles sizes and carbonization degree. The formation mechanism of NCDs is explored: QY of NCDs depends largely on the number of fluorescent polymer chains (FPC), the competition between FPC formation on the surface of NCDs and carbon core growth leads to the change in number of FPC, and consequently to the NCDs with highest QY at appropriate hydrothermal temperature.

  9. Land Cover Differences in Soil Carbon and Nitrogen at Fort Benning, Georgia

    Energy Technology Data Exchange (ETDEWEB)

    Garten Jr., C.T.

    2004-02-09

    Land cover characterization might help land managers assess the impacts of management practices and land cover change on attributes linked to the maintenance and/or recovery of soil quality. However, connections between land cover and measures of soil quality are not well established. The objective of this limited investigation was to examine differences in soil carbon and nitrogen among various land cover types at Fort Benning, Georgia. Forty-one sampling sites were classified into five major land cover types: deciduous forest, mixed forest, evergreen forest or plantation, transitional herbaceous vegetation, and barren land. Key measures of soil quality (including mineral soil density, nitrogen availability, soil carbon and nitrogen stocks, as well as properties and chemistry of the O-horizon) were significantly different among the five land covers. In general, barren land had the poorest soil quality. Barren land, created through disturbance by tracked vehicles and/or erosion, had significantly greater soil density and a substantial loss of carbon and nitrogen relative to soils at less disturbed sites. We estimate that recovery of soil carbon under barren land at Fort Benning to current day levels under transitional vegetation or forests would require about 60 years following reestablishment of vegetation. Maps of soil carbon and nitrogen were produced for Fort Benning based on a 1999 land cover map and field measurements of soil carbon and nitrogen stocks under different land cover categories.

  10. Carbon and Nitrogen Stocks and Humic Fractions in Brazilian Organosols

    Directory of Open Access Journals (Sweden)

    Gustavo Souza Valladares

    Full Text Available ABSTRACT Despite limited geographic expression of Organosols in Brazil, their high carbon storage capacity and natural environmental vulnerability justifies further studies on C and N stocks in these soils and their relationship to the nature of organic matter. Evaluation of physical and chemical properties of organic soils and their ability to store C is important so as to develop sustainable management practices for their preservation. The objectives of the study were to measure the total organic carbon stock (OCst, total nitrogen stock (Nst, and humic fractions in Organosols from different environments and regions of Brazil, and to correlate the data with soil chemical (pH, P, K, Ca2+, Mg2+, Al3+, H+Al, CEC, V and physical properties (soil bulk density, Bd; organic matter density, OMd; total pore space, TPS; minimum residue, MinR; and proportion of mineral matter, MM, and degree of organic matter decomposition (rubbed fiber content; pyrophosphate index, PyI; and von Post index. For that purpose, 18 Organosol profiles, in a total of 49 horizons, were sampled under different land usage and plant coverage conditions. The profiles were located in the following Brazilian states - Alagoas, Bahia, Distrito Federal, Espírito Santo, Mato Grosso do Sul, Minas Gerais, Paraná, Rio de Janeiro, Rio Grande do Sul, Santa Catarina, and São Paulo. The OCst and Nst varied significantly among horizons and profiles. The Organosols exhibited, on average, 203.59 Mg ha-1 OCst and 8.30 Mg ha-1 Nst, and the highest values were found in profiles with pasture usage. The content of the humic fraction (humin, HUM; fulvic acid, FAF; and humic acid, HAF and C storage varied in the soil horizons and profiles according to the degree of decomposition and other factors of soil formation. The OCst, Nst, OMd and the C stocks in the humic fractions were positively correlated. The values of acidity were lower in the soils with higher contents of mineral material, and low p

  11. Impacts of Invasive Pests on Forest Carbon and Nitrogen Dynamics

    Science.gov (United States)

    Lovett, G. M.; Crowley, K. F.

    2014-12-01

    Forests of the U.S. have been subject to repeated invasions of destructive insects and diseases imported from other continents. Like other disturbances, these pests can produce short-term ecosystem effects due to tree mortality, but unlike other disturbances, they often target individual species and therefore can cause long-term species change in the forest. Because tree species vary in their influence on carbon (C) and nitrogen (N) cycles, pest-induced species change can radically alter the biogeochemistry of a forest. In this paper we use both data and modeling to examine how pest-induced species change may alter the C and N cycling in forests of the eastern U.S. We describe a new forest ecosystem model that distinguishes individual tree species and allows species composition to shift over the course of the model run. Results indicate that the mortality of eastern hemlock (Tsuga canadensis) by hemlock woolly adelgid and its replacement by faster-growing species such as black birch (Betula lenta) will reduce forest floor C stocks but increase productivity as the birch become established. Decline of American beech (Fagus grandifolia) from beech bark disease and its replacement by sugar maple (Acer saccharum) is likely to decrease soil C storage and increase N leaching from the ecosystem. Responses to other invasive pests will also be discussed. The magnitude of these species-specific effects on C and N cycling is in many cases larger than direct effects expected from changes in climate and atmospheric N deposition, indicating that species change should be included in models that predict forest ecosystem function under future environmental conditions.

  12. Anthropogenic nitrogen deposition enhances carbon sequestration in boreal soils.

    Science.gov (United States)

    Maaroufi, Nadia I; Nordin, Annika; Hasselquist, Niles J; Bach, Lisbet H; Palmqvist, Kristin; Gundale, Michael J

    2015-08-01

    It is proposed that carbon (C) sequestration in response to reactive nitrogen (Nr ) deposition in boreal forests accounts for a large portion of the terrestrial sink for anthropogenic CO2 emissions. While studies have helped clarify the magnitude by which Nr deposition enhances C sequestration by forest vegetation, there remains a paucity of long-term experimental studies evaluating how soil C pools respond. We conducted a long-term experiment, maintained since 1996, consisting of three N addition levels (0, 12.5, and 50 kg N ha(-1) yr(-1) ) in the boreal zone of northern Sweden to understand how atmospheric Nr deposition affects soil C accumulation, soil microbial communities, and soil respiration. We hypothesized that soil C sequestration will increase, and soil microbial biomass and soil respiration will decrease, with disproportionately large changes expected compared to low levels of N addition. Our data showed that the low N addition treatment caused a non-significant increase in the organic horizon C pool of ~15% and a significant increase of ~30% in response to the high N treatment relative to the control. The relationship between C sequestration and N addition in the organic horizon was linear, with a slope of 10 kg C kg(-1) N. We also found a concomitant decrease in total microbial and fungal biomasses and a ~11% reduction in soil respiration in response to the high N treatment. Our data complement previous data from the same study system describing aboveground C sequestration, indicating a total ecosystem sequestration rate of 26 kg C kg(-1) N. These estimates are far lower than suggested by some previous modeling studies, and thus will help improve and validate current modeling efforts aimed at separating the effect of multiple global change factors on the C balance of the boreal region.

  13. Overexpression of Arabidopsis NLP7 improves plant growth under both nitrogen-limiting and -sufficient conditions by enhancing nitrogen and carbon assimilation.

    Science.gov (United States)

    Yu, Lin-Hui; Wu, Jie; Tang, Hui; Yuan, Yang; Wang, Shi-Mei; Wang, Yu-Ping; Zhu, Qi-Sheng; Li, Shi-Gui; Xiang, Cheng-Bin

    2016-06-13

    Nitrogen is essential for plant survival and growth. Excessive application of nitrogenous fertilizer has generated serious environment pollution and increased production cost in agriculture. To deal with this problem, tremendous efforts have been invested worldwide to increase the nitrogen use ability of crops. However, only limited success has been achieved to date. Here we report that NLP7 (NIN-LIKE PROTEIN 7) is a potential candidate to improve plant nitrogen use ability. When overexpressed in Arabidopsis, NLP7 increases plant biomass under both nitrogen-poor and -rich conditions with better-developed root system and reduced shoot/root ratio. NLP7-overexpressing plants show a significant increase in key nitrogen metabolites, nitrogen uptake, total nitrogen content, and expression levels of genes involved in nitrogen assimilation and signalling. More importantly, overexpression of NLP7 also enhances photosynthesis rate and carbon assimilation, whereas knockout of NLP7 impaired both nitrogen and carbon assimilation. In addition, NLP7 improves plant growth and nitrogen use in transgenic tobacco (Nicotiana tabacum). Our results demonstrate that NLP7 significantly improves plant growth under both nitrogen-poor and -rich conditions by coordinately enhancing nitrogen and carbon assimilation and sheds light on crop improvement.

  14. Nitrogen-doped carbons in Li-S batteries: materials design and electrochemical mechanism

    Directory of Open Access Journals (Sweden)

    Xia eLi

    2014-11-01

    Full Text Available Li-S batteries have been considered as next generation Li batteries due to their high theoretical energy density. Over the past few years, researchers have made significant efforts in breaking through critical bottlenecks which impede the commercialization of Li-S batteries. Beginning with a basic introduction to Li-S systems and their associated mechanism, this review will highlight the application of one specific carbon family, nitrogen-doped carbon materials in sulfur based cathodes. These materials will include nitrogen doped porous carbon, carbon nanotubes, nanofibers and graphene. The article will conclude with a summary of recent research efforts in this field as well as the future prospects for the use of nitrogen-doped carbon materials in Li-S batteries.

  15. Determination of free nitrogen in carbon steels by inert gas fusion method

    Science.gov (United States)

    Tabakov, Ya. I.; Grigorovich, K. V.; Mansurova, E. R.

    2016-07-01

    The possibility to use hot extraction (thermal extraction in a carrier-gas flow) for fractional analysis of nitrogen in carbon steels is shown for cord and reinforcing-bar steels. A rapid procedure is developed for an analysis of free nitrogen in carbon steels. The validity of the analytical procedure is confirmed by high-temperature hydrogen extraction. The data obtained by the two methods correlate well with each other. A sample preparation procedure is developed for the determination of the content of dissolved nitrogen.

  16. Nitrogen-doped dual mesoporous carbon for the selective oxidation of ethylbenzene

    Science.gov (United States)

    Chen, Aibing; Yu, Yifeng; Wang, Rujie; Yu, Yunhong; Zang, Wenwei; Tang, Pei; Ma, Ding

    2015-08-01

    A nanocasting method to fabricate nitrogen-doped dual mesoporous carbon is proposed by the carbonization of nitrile functional ionic liquid (FIL) grafted SBA-15 for the first time. These carbon materials have high nitrogen content (12.8%), large specific surface areas (763 m2 g-1) and uniform rod morphologies, which are derived from FILs grafted on the surface of SBA-15. Furthermore, by adjusting the impregnation amount of ionic liquids on SBA-15, pore structures of these carbon materials can be adjusted from single to dual mesopores. The developed dual mesoporous carbon materials exhibit good catalytic performance in the selective oxidation of ethylbenzene, ascribed to the promoting effects of nitrogen-doping, high surface area and dual mesostructure. It may be concluded that the dual mesostructure has an advantage over a single mesostructure to obtain a fast mass transport rate, resulting in higher acetophenone yield.A nanocasting method to fabricate nitrogen-doped dual mesoporous carbon is proposed by the carbonization of nitrile functional ionic liquid (FIL) grafted SBA-15 for the first time. These carbon materials have high nitrogen content (12.8%), large specific surface areas (763 m2 g-1) and uniform rod morphologies, which are derived from FILs grafted on the surface of SBA-15. Furthermore, by adjusting the impregnation amount of ionic liquids on SBA-15, pore structures of these carbon materials can be adjusted from single to dual mesopores. The developed dual mesoporous carbon materials exhibit good catalytic performance in the selective oxidation of ethylbenzene, ascribed to the promoting effects of nitrogen-doping, high surface area and dual mesostructure. It may be concluded that the dual mesostructure has an advantage over a single mesostructure to obtain a fast mass transport rate, resulting in higher acetophenone yield. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03802b

  17. Carbon-nitrogen place exchange on NO exposed beta-Mo2C.

    Science.gov (United States)

    Siaj, Mohamed; Maltais, Carl; Zahidi, El Mamoune; Oudghiri-Hassani, Hicham; Wang, Jiqing; Rosei, Federico; McBreen, Peter H

    2005-08-18

    Atomic nitrogen and oxygen were deposited on beta-Mo(2)C through dissociative adsorption of NO. Reflectance absorbance infrared spectroscopy (RAIRS), thermal desorption, and synchrotron X-ray photoelectron spectroscopy (XPS) measurements were used to investigate the interplay between atomic nitrogen, carbon, and oxygen in the 400-1250 K region. The combination of the high resolution and high surface sensitivity offered by the synchrotron XPS technique was used to show that atomic nitrogen displaces interstitial carbon onto the carbide surface. Thermal desorption measurements show that the burnoff of the displaced carbon occurs at approximately 890 K. The incorporation of nitrogen into interstitial sites inhibits oxygen dissolution into the bulk. RAIRS spectroscopy was used to identify surface oxo, terminal oxygen, species formed from O(2) and NO on beta-Mo(2)C.

  18. Modeling canopy-level productivity: is the "big-leaf" simplification acceptable?

    Science.gov (United States)

    Sprintsin, M.; Chen, J. M.

    2009-05-01

    The "big-leaf" approach to calculating the carbon balance of plant canopies assumes that canopy carbon fluxes have the same relative responses to the environment as any single unshaded leaf in the upper canopy. Widely used light use efficiency models are essentially simplified versions of the big-leaf model. Despite its wide acceptance, subsequent developments in the modeling of leaf photosynthesis and measurements of canopy physiology have brought into question the assumptions behind this approach showing that big leaf approximation is inadequate for simulating canopy photosynthesis because of the additional leaf internal control on carbon assimilation and because of the non-linear response of photosynthesis on leaf nitrogen and absorbed light, and changes in leaf microenvironment with canopy depth. To avoid this problem a sunlit/shaded leaf separation approach, within which the vegetation is treated as two big leaves under different illumination conditions, is gradually replacing the "big-leaf" strategy, for applications at local and regional scales. Such separation is now widely accepted as a more accurate and physiologically based approach for modeling canopy photosynthesis. Here we compare both strategies for Gross Primary Production (GPP) modeling using the Boreal Ecosystem Productivity Simulator (BEPS) at local (tower footprint) scale for different land cover types spread over North America: two broadleaf forests (Harvard, Massachusetts and Missouri Ozark, Missouri); two coniferous forests (Howland, Maine and Old Black Spruce, Saskatchewan); Lost Creek shrubland site (Wisconsin) and Mer Bleue petland (Ontario). BEPS calculates carbon fixation by scaling Farquhar's leaf biochemical model up to canopy level with stomatal conductance estimated by a modified version of the Ball-Woodrow-Berry model. The "big-leaf" approach was parameterized using derived leaf level parameters scaled up to canopy level by means of Leaf Area Index. The influence of sunlit

  19. Carbon and nitrogen balance of leaf-eating sesarmid crabs ( Neoepisesarma versicolor) offered different food sources

    Science.gov (United States)

    Thongtham, Nalinee; Kristensen, Erik

    2005-10-01

    Carbon and nitrogen budgets for the leaf-eating crab, Neoepisesarma versicolor, were established for individuals living on pure leaf diets. Crabs were fed fresh (green), senescent (yellow) and partly degraded (brown) leaves of the mangrove tree Rhizophora apiculata. Ingestion, egestion and metabolic loss of carbon and nitrogen were determined from laboratory experiments. In addition, bacterial abundance in various compartments of the crabs' digestive tract was enumerated after dissection of live individuals. Ingestion and egestion rates (in terms of dry weight) were highest, while the assimilation efficiency was poorest for crabs fed on brown leaves. The low assimilation efficiency was more than counteracted by the high ingestion rate providing more carbon for growth than for crabs fed green and yellow leaves. In any case, the results show that all types of leaves can provide adequate carbon while nitrogen was insufficient to support both maintenance (yellow leaves) and growth (green, yellow and brown leaves). Leaf-eating crabs must therefore obtain supplementary nitrogen by other means in order to meet their nitrogen requirement. Three hypotheses were evaluated: (1) crabs supplement their diet with bacteria and benthic microalgae by ingesting own faeces and/or selective grazing at the sediment surface; (2) assimilation of symbiotic nitrogen-fixing bacteria in the crabs' own intestinal system; and (3) nitrogen storage following occasional feeding on animal tissues (e.g. meiofauna and carcasses). It appears that hypothesis 1 is of limited importance for N. versicolor since faeces and sediment can only supply a minor fraction of the missing nitrogen due to physical constraints on the amount of material the crabs can consume. Hypothesis 2 can be ruled out because tests showed no nitrogen fixation activity in the intestinal system of N. versicolor. It is therefore likely that leaf-eating crabs provide most of their nitrogen requirement from intracellular deposits

  20. Contributions of secondary forest and nitrogen dynamics to terrestrial carbon uptake

    Directory of Open Access Journals (Sweden)

    X. Yang

    2010-04-01

    Full Text Available We use a terrestrial carbon-nitrogen cycle component of the Integrated Science Assessment Model (ISAM to investigate the impacts of nitrogen dynamics on regrowing secondary forests over the 20th century. We further examine what the impacts of nitrogen deposition and land use change history are on terrestrial carbon uptake since preindustrial time. Our results suggest that global total net land use emissions for the 1990s associated with changes in cropland, pastureland, and wood harvest are 1.22 GtC/yr. Without considering the secondary forest regrowth, the estimated net global total land use emissions are 1.58 GtC/yr or about 0.36 GtC/yr higher than if secondary forest regrowth is considered. Results also show that without considering the nitrogen dynamics and deposition, the estimated global total secondary forest sink for the 1990s is 0.90 GtC/yr or about 0.54 GtC/yr higher than estimates that include the impacts of nitrogen dynamics and deposition. Nitrogen deposition alone is responsible for about 0.13 GtC/yr of the total secondary forest sink. While nitrogen is not a limiting nutrient in the intact primary forests in tropical regions, our study suggests that nitrogen becomes a limiting nutrient for regrowing secondary forests of the tropical regions, in particular Latin America and Tropical Africa. This is because land use change activities, especially wood harvest, removes large amounts of nitrogen from the system when slash is burnt or wood is removed for harvest. However, our model results show that carbon uptake is enhanced in the tropical secondary forests of the Indian region. We argue that this may be due to enhanced nitrogen mineralization and increased nitrogen availability following land use change in the Indian tropical forest ecosystems. Results also demonstrate that there is a significant amount of carbon accumulating in the Northern Hemisphere where most land use changes and forest regrowth has occurred in recent decades

  1. The impact of nitrogen deposition on carbon sequestration by European forests and heathlands

    NARCIS (Netherlands)

    Vries, de W.; Solberg, S.; Dobbertin, M.; Sterba, H.; Laubhann, D.; Oijen, van M.; Evans, C.; Gundersen, P.; Kros, H.; Wamelink, W.; Reinds, G.J.; Sutton, M.A.

    2009-01-01

    In this study, we present estimated ranges in carbon (C) sequestration per kg nitrogen (N) addition in above-ground biomass and in soil organic matter for forests and heathlands, based on: (i) empirical relations between spatial patterns of carbon uptake and influencing environmental factors includi

  2. Modeling of carbon and nitrogen gaseous emissions from cattle manure compost windrows

    Science.gov (United States)

    Windrow composting of cattle manure is a significant source of gaseous emissions, which include ammonia (NH3) and the greenhouse gases (GHGs) of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). A manure compost model was developed to simulate carbon (C) and nitrogen (N) processes includ...

  3. Variation of fluxes of water vapor, sensible heat and carbon dioxide above winter wheat and maize canopies

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Surface energy fluxes were measured using Bowen-Ratio Energy Balance technique (BREB) and eddy correlation system at Luancheng of Hebei Province, on the North China Plain from 1999 to 2001. Average diumal variation of surface energy fluxes and CO2 flux for maize showed the inverse "U "type. The average peak fluxes did not appear at noon, but after noon. The average peak CO2 flux was about 1.65 mgm-2 s-1. Crop water use efficiency (WUE) increased quickly in the morning, stabilized after 10:00 and decreased quickly after 15:00 with no evident peak value. The ratio of latent heat flux (λE) to net solar radiation (Rn) was always higher than 70% during winter wheat and maize seasons. The seasonal average ratio of sensible heat flux (H) divided by Rn stayed at about 15% above the field surface; the seasonal average ratio of conductive heat flux (G) divided by Rn varied between 5% and 13%, and the average G/Rn from the wheat canopy was evidently higher than that from the maize canopy. The evaporative fraction (EF) is correlated to the Bowen ratio in a reverse function. EF for winter wheat increased quickly during that revival stage, after the stage, it gradually stabilized to 1.0, and fluctuated around 1.0. EF for maize also fluctuated around 1.0 before the later grain filling stage, and decreased after that stage.

  4. Nitrogen removal from coal gasification wastewater by activated carbon technologies combined with short-cut nitrogen removal process.

    Science.gov (United States)

    Zhao, Qian; Han, Hongjun; Hou, Baolin; Zhuang, Haifeng; Jia, Shengyong; Fang, Fang

    2014-11-01

    A system combining granular activated carbon and powdered activated carbon technologies along with shortcut biological nitrogen removal (GAC-PACT-SBNR) was developed to enhance total nitrogen (TN) removal for anaerobically treated coal gasification wastewater with less need for external carbon resources. The TN removal efficiency in SBNR was significantly improved by introducing the effluent from the GAC process into SBNR during the anoxic stage, with removal percentage increasing from 43.8%-49.6% to 68.8%-75.8%. However, the TN removal rate decreased with the progressive deterioration of GAC adsorption. After adding activated sludge to the GAC compartment, the granular carbon had a longer service-life and the demand for external carbon resources became lower. Eventually, the TN removal rate in SBNR was almost constant at approx. 43.3%, as compared to approx. 20.0% before seeding with sludge. In addition, the production of some alkalinity during the denitrification resulted in a net savings in alkalinity requirements for the nitrification reaction and refractory chemical oxygen demand (COD) degradation by autotrophic bacteria in SBNR under oxic conditions. PACT showed excellent resilience to increasing organic loadings. The microbial community analysis revealed that the PACT had a greater variety of bacterial taxons and the dominant species associated with the three compartments were in good agreement with the removal of typical pollutants. The study demonstrated that pre-adsorption by the GAC-sludge process could be a technically and economically feasible method to enhance TN removal in coal gasification wastewater (CGW).

  5. Nitrogen and carbon interactions in controlling terrestrial greenhouse gas fluxes

    Science.gov (United States)

    Ineson, Phil; Toet, Sylvia; Christiansen, Jesper

    2016-04-01

    The increased input of N to terrestrial systems may have profound impacts on net greenhouse gas (GHGs) fluxes and, consequently, our future climate; however, fully capturing and quantifying these interactions under field conditions urgently requires new, more efficient, measurement approaches. We have recently developed and deployed a novel system for the automation of terrestrial GHG flux measurements at the chamber and plot scales, using the approach of 'flying' a single measurement chamber to multiple points in an experimental field arena. As an example of the value of this approach, we shall describe the results from a field experiment investigating the interactions between increasing inorganic nitrogen (N) and carbon (C) additions on net ecosystem exchanges of N2O, CH4 and CO2, enabling the simultaneous application of 25 treatments, replicated five times in a fully replicated block field design. We will describe how the ability to deliver automated GHG flux measurements, highly replicated in space and time, has revealed hitherto unreported findings on N and C interactions in field soil. In our experiments we found insignificant N2O fluxes from bare field soil, even at very high inorganic N addition rates, but the interactive addition of even small amounts of available C resulted in very large and rapid N2O fluxes. The SkyGas experimental system enabled investigation of the underlying interacting response surfaces on the fluxes of the major soil-derived GHGs (CO2, CH4 and N2O) to increasing N and C inputs, and revealed unexpected interactions. In addition to these results we will also discuss some of the technical problems which have been overcome in developing these 'flying' systems and the potential of the systems for automatically screening the impacts of large numbers of treatments on GHG fluxes, and other ecosystem responses, under field conditions. We describe here technological advances that can facilitate the development of more robust GHG mitigation

  6. Soil carbon and nitrogen stocks following forest conversion to pasture in the Western Brazilian Amazon Basin

    OpenAIRE

    2008-01-01

    We examined two chronosequences of forest, 8-and 20-year-old pasture in Rondônia-Brazil, to investigate how land use change affects the soil carbon and nitrogen stocks and organic matter dynamics of surface soil (0 to 30 cm). Soil total carbon and nitrogen stocks increased in 20-year-old pasture compared with the original forest in one chronosequence but no changes were detected in the other chronosequence. Calculations of the contributions of forest - and pasture-derived carbon from soil &et...

  7. Soil properties in forest gaps and under canopy in broad-leaved Pinus koraiensis forests in Changbai Mountainous Region, China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chunyu; ZHAO Xiuhai

    2007-01-01

    The species composition and diversities,and soil properties under canopy gaps in broad-leaved Pinus koraiensis forests were studied in the Changbai Mountains.The results indicated that the species composition and diversifies in gap were different from those under canopy.The Shannon-Wiener index,evenness index,and abundance index in gap were higher than those under canopy in the seedling layer,while the community dominance in the seedling layer increased in closed canopy.The physicochemical properties of soil changed with the change of space and resource availability in gaps.The thickness,standing crop,and water holding capacity of the litter layer under canopy were significantly (p < 0.01) higher than those in gap.The content of total nitrogen and total potassium of litter in gap were 10.47% and 20.73% higher than those under canopy,however,the content of total phosphorus and organic carbon under canopy were 15.23% and 12.66% more than those under canopy.The water content of 0-10 cm and 10-20 cm of soil layer in gap were 17.65% and 16.17% more than those under canopy.The soil buck density of 0-10 cm were slightly higher under canopy than that in gaps,but there was no significant difference in the soil buck density of the 10-20 cm soil layer.The soil pH values were 5.80 and 5.85 in gap and under canopy,respectively,and were not significantly different.The content of soil organic matter,total nitrogen,and total potassium in gap were 12.85%,7.67%,and 2.38% higher than those under canopy.The content of NH4+-N,available phosphorus,available potassium,and total phosphorus in soil under canopy were 13.33%,20.04%,16.52%,and 4.30% higher than those in gap.

  8. Fast Conversion of Ionic Liquids and Poly(Ionic Liquid)s into Porous Nitrogen-Doped Carbons in Air

    OpenAIRE

    2016-01-01

    Ionic liquids and poly(ionic liquid)s have been successfully converted into nitrogen-doped porous carbons with tunable surface area up to 1200 m2/g at high temperatures in air. Compared to conventional carbonization process conducted under inert gas to produce nitrogen-doped carbons, the new production method was completed in a rather shorter time without noble gas protection.

  9. Numerical sensitivity study of the nocturnal low-level jet over a forest canopy and implications for nocturnal surface exchange of carbon dioxide and other trace gases

    DEFF Research Database (Denmark)

    Sogachev, Andrey; Leclerc, M.Y.; Duarte, H.F.

    2010-01-01

    in the nocturnal boundary layer, several studies demonstrated the role of nocturnal jets in transporting moisture, ozone, and other trace gases between the biosphere and the lower atmosphere (Mathieu et al., 2005; Karipot et al., 2006; 2007; 2008; 2009). This study suggests that SCADIS, because of its simplicity...... and low computational demand, has potential as a research tool regarding surface–atmosphere gaseous exchange in the nocturnal boundary layer, especially if carbon dioxide, water vapor, ozone and other gases are released or deposited inside the forest canopy.......The development of a wind speed maximum in the nocturnal boundary layer, commonly referred to as a low-level jet (LLJ) (Blackadar, 1957), is a common feature of the vertical structure of the atmospheric boundary layer (ABL) and impacts the meteorology and the local climate of a region. A variety...

  10. Forest management in Earth system modelling: a vertically discretised canopy description for ORCHIDEE and the modifications to the energy, water and carbon fluxes

    Science.gov (United States)

    Naudts, Kim; Ryder, James; McGrath, Matthew J.; Otto, Juliane; Chen, Yiying; Valade, Aude; Bellasen, Valentin; Ghattas, Josefine; Haverd, Vanessa; MacBean, Natasha; Maignan, Fabienne; Peylin, Philippe; Pinty, Bernard; Solyga, Didier; Vuichard, Nicolas; Luyssaert, Sebastiaan

    2015-04-01

    Since 70% of global forests are managed and forests impact the global carbon cycle and the energy exchange with the overlying atmosphere, forest management has the potential to mitigate climate change. Yet, none of the land surface models used in Earth system models, and therefore none of today's predictions of future climate, account for the interactions between climate and forest management. We addressed this gap in modelling capability by developing and parametrizing a version of the land surface model ORCHIDEE to simulate the biogeochemical and biophysical effects of forest management. The most significant changes between the new model called ORCHIDEE-CAN and the standard version of ORCHIDEE are the allometric-based allocation of carbon to leaf, root, wood, fruit and reserve pools; the transmittance, absorbance and reflectance of radiation within the canopy; and the vertical discretisation of the energy budget calculations. In addition, conceptual changes towards a better process representation occurred for the interaction of radiation with snow, the hydraulic architecture of plants, the representation of forest management and a numerical solution for the photosynthesis formalism of Farquhar, von Caemmerer and Berry. For consistency reasons, these changes were extensively linked throughout the code. Parametrization was revisited after introducing twelve new parameter sets that represent specific tree species or genera rather than a group of unrelated species, as is the case in widely used plant functional types. Performance of the new model was compared against the trunk and validated against independent spatially explicit data for basal area, tree height, canopy structure, GPP, albedo and evapotranspiration over Europe. For all tested variables ORCHIDEE-CAN outperformed the trunk regarding its ability to reproduce large-scale spatial patterns as well as their inter-annual variability over Europe. Depending on the data stream, ORCHIDEE-CAN had a 67 to 92

  11. Nitrogen Dynamics are a Key Factor in Explaining Global Land Carbon Sink

    Science.gov (United States)

    Huntzinger, D. N.; Michalak, A. M.; Schwalm, C.; Ciais, P.; Schaefer, K. M.; King, A. W.; Wei, Y.; Cook, R. B.; Fisher, J. B.; Hayes, D. J.; Huang, M.; Ito, A.; Jain, A. K.; Lei, H.; Lu, C.; Maignan, F.; Mao, J.; Parazoo, N.; Peng, S.; Poulter, B.; Ricciuto, D. M.; Shi, X.; Tian, H.; Wang, W.; Zeng, N.; Zhao, F.

    2015-12-01

    The terrestrial carbon cycle plays a critical role in regulating the amount of anthropogenic emissions that remain in the atmosphere. Yet, land-atmosphere carbon dynamics are one of the largest sources of uncertainty in projections of future climate. Reducing this uncertainty requires understanding the relative role of various drivers to land carbon uptake. We use an ensemble of land surface models to quantify the influence of climate, land use history, atmospheric CO2, and nitrogen deposition on the strength of the net land sink over the past 110 years. Each model can be thought of as one realization of terrestrial carbon cycling and the factors most important in controlling land sink strength. Using a series of sensitivity simulations, we identify the dominant drivers to the net land sink that emerge consistently across models, both globally and regionally. We find that the relative importance of external forcing factors on the strength of net land carbon uptake varies considerably across models and depends strongly on whether nitrogen cycling is explicitly simulated. Models without a nitrogen cycle estimate cumulative land carbon uptake (since 1959) that is 3 times greater (93.3 ± 84.1 PgC) than global mass balance constraints (34.6 ± 41.6 PgC). Surprisingly, the greatest impacts are seen in the tropics, where coupled carbon-nitrogen cycle models estimate CO2 fertilization and climate affects that are ~60% weaker than models without a nitrogen cycle. The results highlight the importance of model structure on the inferred sensitivity of land carbon uptake to external forcing factors. The range in sensitivity across models is important for future climate projections since the differences in the processes that explain trends in net land sink strength between models with and without nitrogen dynamics can lead to very different future trajectories of atmospheric CO2 and thus climate.

  12. Green synthesis of luminescent nitrogen-doped carbon dots from milk and its imaging application.

    Science.gov (United States)

    Wang, Li; Zhou, H Susan

    2014-09-16

    In the present work, a completely green synthetic method for producing fluorescent nitrogen-doped carbon dots by using milk is introduced. The process is environmentally friendly, simple, and efficient. By hydrothermal heating of milk, we produced monodispersed, highly fluorescent carbon dots with a size of about 3 nm. Imaging of U87 cells, a human brain glioma cancer cell line, can be easily achieved with high resolution using the prepared carbon dots as probes and validates their use in imaging applications.

  13. Nitrogen-incorporated ultrananocrystalline diamond and multi-layer-graphene-like hybrid carbon films

    Science.gov (United States)

    Tzeng, Yonhua; Yeh, Shoupu; Fang, Wei Cheng; Chu, Yuehchieh

    2014-03-01

    Nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) and multi-layer-graphene-like hybrid carbon films have been synthesized by microwave plasma enhanced chemical vapor deposition (MPECVD) on oxidized silicon which is pre-seeded with diamond nanoparticles. MPECVD of N-UNCD on nanodiamond seeds produces a base layer, from which carbon structures nucleate and grow perpendicularly to form standing carbon platelets. High-resolution transmission electron microscopy and Raman scattering measurements reveal that these carbon platelets are comprised of ultrananocrystalline diamond embedded in multilayer-graphene-like carbon structures. The hybrid carbon films are of low electrical resistivity. UNCD grains in the N-UNCD base layer and the hybrid carbon platelets serve as high-density diamond nuclei for the deposition of an electrically insulating UNCD film on it. Biocompatible carbon-based heaters made of low-resistivity hybrid carbon heaters encapsulated by insulating UNCD for possible electrosurgical applications have been demonstrated.

  14. [Effects of different fertilizer species on carbon and nitrogen leaching in a reddish paddy soil].

    Science.gov (United States)

    Liu, Xi-Yu; Zou, Jing-Dong; Xu, Li-Li; Zhang, Xin-Yu; Yang, Feng-Ting; Dai, Xiao-Qin; Wang, Zhong-Qiang; Sun, Xiao-Min

    2014-08-01

    Enhanced fertilization could decrease nitrogen utilization rate and increase carbon and nitrogen leaching, leading to water pollution in agricultural ecosystem. A long-term field experiment had been established on a reddish paddy soil of Qianyanzhou Ecological Experimental Station (114 degrees 53'E, 26 degrees 48'N) in Jiangxi Province in 1998. Soil solution samples were collected by clay tube and vacuum pump. Four fertilizer species treatments were selected: control with no fertilizer (CK), straw return (ST), nitrogen, phosphorus and potassium mineral fertilizers (NPK) and pig manure (OM), aiming to evaluate the effects of different species of fertilizer on carbon and nitrogen leaching in a double rice cropping system. The results showed that: (1) ammonium nitrogen (NH4(+) -N) was the major type of N in soil leachate in reddish paddy soil. The application of NPK could significantly increase the ammonium nitrogen concentration (1.2 mg x L(-1) +/- 0.1 mg x L(-1)) compared with the CK, ST and OM treatments, and the application of OM could significantly increase the dissolved organic carbon (DOC) concentration (27.3 mg x L(-1) +/- 1.6 mg x L(-1)) in soil leachate. The carbon and nitrogen leaching were more notable in the vegetative growth stage than the reproductive growth stage of rice (P soil organic carbon (SOC) and total nitrogen (TN) contents. The NPK was best beneficial to improve TN contents and OM to improve SOC contents. (3) The DOC contents in soil leachate and SOC in paddy soil had a positive correlation (P soil leachate and TN contents in paddy soil had a positive correlation (P < 0.01).

  15. Nitrogen

    Science.gov (United States)

    Apodaca, Lori E.

    2013-01-01

    The article presents an overview of the nitrogen chemical market as of July 2013, including the production of ammonia compounds. Industrial uses for ammonia include fertilizers, explosives, and plastics. Other topics include industrial capacity of U.S. ammonia producers CF Industries Holdings Inc., Koch Nitrogen Co., PCS Nitrogen, Inc., and Agrium Inc., the impact of natural gas prices on the nitrogen industry, and demand for corn crops for ethanol production.

  16. Responses of Carbon Dynamics to Nitrogen Deposition in Typical Freshwater Wetland of Sanjiang Plain

    Directory of Open Access Journals (Sweden)

    Yang Wang

    2014-01-01

    Full Text Available The effects of nitrogen deposition (N-deposition on the carbon dynamics in typical Calamagrostis angustifolia wetland of Sanjiang Plain were studied by a pot-culture experiment during two continuous plant growing seasons. Elevated atmospheric N-deposition caused significant increases in the aboveground net primary production and root biomass; moreover, a preferential partition of carbon to root was also observed. Different soil carbon fractions gained due to elevated N-deposition and their response intensities followed the sequence of labile carbon > dissolved organic carbon > microbial biomass carbon, and the interaction between N-deposition and flooded condition facilitated the release of different carbon fractions. Positive correlations were found between CO2 and CH4 fluxes and liable carbon contents with N-deposition, and flooded condition also tended to facilitate CH4 fluxes and to inhibit the CO2 fluxes with N-deposition. The increases in soil carbon fractions occurring in the nitrogen treatments were significantly correlated with increases in root, aboveground parts, total biomass, and their carbon uptake. Our results suggested that N-deposition could enhance the contents of active carbon fractions in soil system and carbon accumulation in plant of the freshwater wetlands.

  17. Palladium on Nitrogen-Doped Mesoporous Carbon: A Bifunctional Catalyst for Formate-Based, Carbon-Neutral Hydrogen Storage.

    Science.gov (United States)

    Wang, Fanan; Xu, Jinming; Shao, Xianzhao; Su, Xiong; Huang, Yanqiang; Zhang, Tao

    2016-02-08

    The lack of safe, efficient, and economical hydrogen storage technologies is a hindrance to the realization of the hydrogen economy. Reported herein is a reversible formate-based carbon-neutral hydrogen storage system that is established over a novel catalyst comprising palladium nanoparticles supported on nitrogen-doped mesoporous carbon. The support was fabricated by a hard template method and nitridated under a flow of ammonia. Detailed analyses demonstrate that this bicarbonate/formate redox equilibrium is promoted by the cooperative role of the doped nitrogen functionalities and the well-dispersed, electron-enriched palladium nanoparticles.

  18. Biophysical Controls over Carbon and Nitrogen Stocks in Desert Playa Wetlands

    Science.gov (United States)

    McKenna, O. P.; Sala, O. E.

    2014-12-01

    Playas are ephemeral desert wetlands situated at the bottom of closed catchments. Desert playas in the Southwestern US have not been intensively studied despite their potential importance for the functioning of desert ecosystems. We want to know which geomorphic and ecological variables control of the stock size of soil organic carbon, and soil total nitrogen in playas. We hypothesize that the magnitude of carbon and nitrogen stocks depends on: (a) catchment size, (b) catchment slope, (d) catchment vegetation cover, (e) bare-ground patch size, and (f) catchment soil texture. We chose thirty playas from across the Jornada Basin (Las Cruces, NM) ranging from 0.5-60ha in area and with varying catchment characteristics. We used the available 5m digital elevation map (DEM) to calculate the catchment size and catchment slope for these thirty playas. We measured percent cover, and patch size using the point-intercept method with three 10m transects in each catchment. We used the Bouyoucos-hydrometer soil particle analysis to determine catchment soil texture. Stocks of organic carbon and nitrogen were measured from soil samples at four depths (0-10 cm, 10-30 cm, 30-60 cm, 60-100 cm) using C/N combustion analysis. In terms of nitrogen and organic carbon storage, we found soil nitrogen values in the top 10cm ranging from 41.963-214.365 gN/m2, and soil organic carbon values in the top 10cm ranging from 594.339-2375.326 gC/m2. The results of a multiple regression analysis show a positive relationship between catchment slope and both organic carbon and nitrogen stock size (nitrogen: y= 56.801 +47.053, R2=0.621; organic carbon: y= 683.200 + 499.290x, R2= 0.536). These data support our hypothesis that catchment slope is one of factors controlling carbon and nitrogen stock in desert playas. We also applied our model to the 69 other playas of the Jornada Basin and estimated stock sizes (0-10cm) between 415.07-447.97 Mg for total soil nitrogen and 4627.99-5043.51 Mg for soil organic

  19. [Relationship between Fe, Al oxides and stable organic carbon, nitrogen in the yellow-brown soils].

    Science.gov (United States)

    Heng, Li-Sha; Wang, Dai-Zhang; Jiang, Xin; Rao, Wei; Zhang, Wen-Hao; Guo, Chun-Yan; Li, Teng

    2010-11-01

    The stable organic carbon and nitrogen of the different particles were gained by oxidation of 6% NaOCl in the yellow-brown soils. The relationships between the contents of selective extractable Fe/Al and the stable organic carbon/nitrogen were investigated. It shown that amounts of dithionite-citrate-(Fe(d)) and oxalate-(Fe(o)) and pyrophosphate extractable (Fe(p)) were 6-60.8 g x kg(-1) and 0.13-4.8 g x kg(-1) and 0.03-0.47 g x kg(-1) in 2-250 microm particles, respectively; 43.1-170 g x kg(-1) and 5.9-14.0 g x kg(-1) and 0.28-0.78 g x kg(-1) in soils than in arid yellow-brown soils, and that of selective extractable Al are lower in the former than in the latter. Amounts of the stable organic carbon and nitrogen, higher in paddy yellow-brown soils than in arid yellow-brown soils, were 0.93-6.0 g x kg(-1) and 0.05-0.36 g x kg(-1) in 2-250 microm particles, respectively; 6.05-19.3 g x kg(-1) and 0.61-2.1 g x kg(-1) in organic carbon and nitrogen (C(stable)/N(stable)) were 9.50-22.0 in 2-250 microm particles and 7.43-11.54 in organic carbon and nitrogen were 14.3-50.0 and 11.9-55.6 in 2-250 microm particles, respectively; 53.72-88.80 and 40.64-70.0 in soils than in paddy yellow-brown soils. The organic carbon and nitrogen are advantageously conserved in paddy yellow-brown soil. An extremely significant positive correlation of the stable organic carbon and nitrogen with selective extractable Fe/Al is observed. The most amounts between the stable organic carbon and nitrogen and selective extractable Fe/Al appear in clay particles, namely the clay particles could protect the soil organic carbon and nitrogen.

  20. Carbon and nitrogen isotopic signatures and nitrogen profile to identify adulteration in organic fertilizers.

    Science.gov (United States)

    Verenitch, Sergei; Mazumder, Asit

    2012-08-29

    Recently it has been shown that stable isotopes of nitrogen can be used to discriminate between organic and synthetic fertilizers, but the robustness of the approach is questionable. This work developed a comprehensive method that is far more robust in identifying an adulteration of organic nitrogen fertilizers. Organic fertilizers of various types (manures, composts, blood meal, bone meal, fish meal, products of poultry and plant productions, molasses and seaweed based, and others) available on the North American market were analyzed to reveal the most sensitive criteria as well as their quantitative ranges, which can be used in their authentication. Organic nitrogen fertilizers of known origins with a wide δ(15)N range between -0.55 and 28.85‰ (n = 1258) were characterized for C and N content, δ(13)C, δ(15)N, viscosity, pH, and nitrogen profile (urea, ammonia, organic N, water insoluble N, and NO3). A statistically significant data set of characterized unique organic nitrogen fertilizers (n = 335) of various known origins has been assembled. Deliberately adulterated samples of different types of organic fertilizers mixed with synthetic fertilizers at a wide range of proportions have been used to develop the quantitative critical characteristics of organic fertilizers as the key indicators of their adulteration. Statistical analysis based on the discriminant functions of the quantitative critical characteristics of organic nitrogen fertilizers from 14 different source materials revealed a very high average rate of correct classification. The developed methodology has been successfully used as a source identification tool for numerous commercial nitrogen fertilizers available on the North American market.

  1. Nitrogen-Doped Carbon Dots as A New Substrate for Sensitive Glucose Determination

    Directory of Open Access Journals (Sweden)

    Hanxu Ji

    2016-05-01

    Full Text Available Nitrogen-doped carbon dots are introduced as a novel substrate suitable for enzyme immobilization in electrochemical detection metods. Nitrogen-doped carbon dots are easily synthesised from polyacrylamide in just one step. With the help of the amino group on chitosan, glucose oxidase is immobilized on nitrogen-doped carbon dots-modified carbon glassy electrodes by amino-carboxyl reactions. The nitrogen-induced charge delocalization at nitrogen-doped carbon dots can enhance the electrocatalytic activity toward the reduction of O2. The specific amino-carboxyl reaction provides strong and stable immobilization of GOx on electrodes. The developed biosensor responds efficiently to the presence of glucose in serum samples over the concentration range from 1 to 12 mM with a detection limit of 0.25 mM. This novel biosensor has good reproducibility and stability, and is highly selective for glucose determination under physiological conditions. These results indicate that N-doped quantum dots represent a novel candidate material for the construction of electrochemical biosensors.

  2. Modelling Plant and Soil Nitrogen Feedbacks Affecting Forest Carbon Gain at High CO2

    Science.gov (United States)

    McMurtrie, R. E.; Norby, R. J.; Franklin, O.; Pepper, D. A.

    2007-12-01

    Short-term, direct effects of elevated atmospheric CO2 concentrations on plant carbon gain are relatively well understood. There is considerable uncertainty, however, about longer-term effects, which are influenced by various plant and ecosystem feedbacks. A key feedback in terrestrial ecosystems occurs through changes in plant carbon (C) allocation patterns. For instance, if high CO2 were to increase C allocation to roots, then plants may experience positive feedback through improved plant nutrition. A second type of feedback, associated with decomposition of soil-organic matter, may reduce soil-nutrient availability at high CO2. This paper will consider mechanistic models of both feedbacks. Effects of high CO2 on plant C allocation will be investigated using a simple model of forest net primary production (NPP) that incorporates the primary mechanisms of plant carbon and nitrogen (N) balance. The model called MATE (Model Any Terrestrial Ecosystem) includes an equation for annual C balance that depends on light- saturated photosynthetic rate and therefore on [CO2], and an equation for N balance incorporating an expression for N uptake as a function of root mass. The C-N model is applied to a Free Air CO2 Exchange (FACE) experiment at Oak Ridge National Laboratory (ORNL) in Tennessee, USA, where closed-canopy, monoculture stands of the deciduous hardwood sweetgum ( Liquidambar styraciflua) have been growing at [CO2] of 375 and 550 ppm for ten years. Features of this experiment are that the annual NPP response to elevated CO2 has averaged approximately 25% over seven years, but that annual fine-root production has almost doubled on average, with especially large increases in later years of the experiment (Norby et al. 2006). The model provides a simple graphical approach for analysing effects of elevated CO2 and N supply on leaf/root/wood C allocation and productivity. It simulates increases in NPP and fine-root production at the ORNL FACE site that are consistent

  3. Improving representation of nitrogen uptake, allocation, and carbon assimilation in the Community Land Model

    Science.gov (United States)

    Ghimire, B.; Riley, W. J.; Koven, C.

    2013-12-01

    Nitrogen is the most important nutrient limiting plant carbon assimilation and growth, and is required for production of photosynthetic enzymes, growth and maintenance respiration, and maintaining cell structure. The forecasted rise in plant available nitrogen through atmospheric nitrogen deposition and the release of locked soil nitrogen by permafrost thaw in high latitude ecosystems is likely to result in an increase in plant productivity. However a mechanistic representation of plant nitrogen dynamics is lacking in earth system models. Most earth system models ignore the dynamic nature of plant nutrient uptake and allocation, and further lack tight coupling of below- and above-ground processes. In these models, the increase in nitrogen uptake does not translate to a corresponding increase in photosynthesis parameters, such as maximum Rubisco capacity and electron transfer rate. We present an improved modeling framework implemented in the Community Land Model version 4.5 (CLM4.5) for dynamic plant nutrient uptake, and allocation to different plant parts, including leaf enzymes. This modeling framework relies on imposing a more realistic flexible carbon to nitrogen stoichiometric ratio for different plant parts. The model mechanistically responds to plant nitrogen uptake and leaf allocation though changes in photosynthesis parameters. We produce global simulations, and examine the impacts of the improved nitrogen cycling. The improved model is evaluated against multiple observations including TRY database of global plant traits, nitrogen fertilization observations and 15N tracer studies. Global simulations with this new version of CLM4.5 showed better agreement with the observations than the default CLM4.5-CN model, and captured the underlying mechanisms associated with plant nitrogen cycle.

  4. Effect of Nitrogen Source and Carbon to Nitrogen Ratio on Hydrogen Production using C. acetobutylicum

    Directory of Open Access Journals (Sweden)

    Mohd Sahaid Kalil

    2008-01-01

    Full Text Available Problem statement: One of the main factors influenced the bacterial productivity and total yield of hydrogen is the nitrogen source and its concentration. Approach: Using different nitrogen source with different concentration on bacterial productivity of hydrogen showed to affect on both bacterial productivity of hydrogen and biomass concentration. Results: Yeast extract as nitrogen source at concentration of 13 g L-1 was the best organic nitrogen source and resulted in hydrogen yield YP/S of 308 mL g-1 glucose utilized with biomass concentration of 1.1 g L-1, hydrogen yield per biomass YP/X of 280 mL g-1 L-1, biomass per substrate utilized YX/S of 0.22 and produced hydrogen in gram per gram of glucose utilized YH2/S of 0.0275. C/N of 70 enhanced the YP/S from 308-350 mL g?1 glucose utilized with biomass concentration of 1.22 gL-1, YP/X of 287 mL g-1 L-1, YX/S of 0.244 and YH2/S of 0.03125. Conclusion: Nitrogen source with proper C:N ratio enhanced the hydrogen production.

  5. Carbon and nitrogen fluxes in the North Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Naik, H.; DeSouza, W.; Narvekar, P.V.; Paropkari, A.L.; Bange, H.W.

    of intense water column denitrification (Deutsch et al., 2007). Substantial N 2 -fixation is also believed to occur within the Red Sea as evident from the high N:P uptake/regeneration ratio (~21). Based on the exchanges of nutrients and water across the Bab..., Yoshinari T (2001) The oceanic fixed nitrogen and nitrous oxide budgets: Moving targets as we enter the anthropocene. Sci Mar 65 (Suppl.): 85-105 Deutsch C, Sarmiento JL, Sigman DM, Gruber N, Dunne JP (2007) Spatial coupling of nitrogen inputs and losses...

  6. Canopy Dynamics in Nanoscale Ionic Materials

    KAUST Repository

    Jespersen, Michael L.

    2010-07-27

    Nanoscale ionic materials (NIMS) are organic - inorganic hybrids in which a core nanostructure is functionalized with a covalently attached corona and an ionically tethered organic canopy. NIMS are engineered to be liquids under ambient conditions in the absence of solvent and are of interest for a variety of applications. We have used nuclear magnetic resonance (NMR) relaxation and pulse-field gradient (PFG) diffusion experiments to measure the canopy dynamics of NIMS prepared from 18-nm silica cores modified by an alkylsilane monolayer possessing terminal sulfonic acid functionality, paired with an amine-terminated ethylene oxide/propylene oxide block copolymer canopy. Carbon NMR studies show that the block copolymer canopy is mobile both in the bulk and in the NIMS and that the fast (ns) dynamics are insensitive to the presence of the silica nanoparticles. Canopy diffusion in the NIMS is slowed relative to the neat canopy, but not to the degree predicted from the diffusion of hard-sphere particles. Canopy diffusion is not restricted to the surface of the nanoparticles and shows unexpected behavior upon addition of excess canopy. Taken together, these data indicate that the liquid-like behavior in NIMS is due to rapid exchange of the block copolymer canopy between the ionically modified nanoparticles. © 2010 American Chemical Society.

  7. Nitrogen-doped mesoporous carbon of extraordinary capacitance for electrochemical energy storage

    Science.gov (United States)

    Lin, Tianquan; Chen, I.-Wei; Liu, Fengxin; Yang, Chongyin; Bi, Hui; Xu, Fangfang; Huang, Fuqiang

    2015-12-01

    Carbon-based supercapacitors can provide high electrical power, but they do not have sufficient energy density to directly compete with batteries. We found that a nitrogen-doped ordered mesoporous few-layer carbon has a capacitance of 855 farads per gram in aqueous electrolytes and can be bipolarly charged or discharged at a fast, carbon-like speed. The improvement mostly stems from robust redox reactions at nitrogen-associated defects that transform inert graphene-like layered carbon into an electrochemically active substance without affecting its electric conductivity. These bipolar aqueous-electrolyte electrochemical cells offer power densities and lifetimes similar to those of carbon-based supercapacitors and can store a specific energy of 41 watt-hours per kilogram (19.5 watt-hours per liter).

  8. Structural investigation of two carbon nitride solids produced by cathodic arc deposition and nitrogen implantation

    Energy Technology Data Exchange (ETDEWEB)

    Merchant, A.R.; McCulloch, D.; McKenzie, D.R.; Yin, Y.; Gerstner, E.G. [New South Wales Univ., Kensington, NSW (Australia)

    1996-12-31

    Carbon nitride materials have been the focus of research efforts worldwide. Most materials studied have been amorphous, with only a few groups claiming to have found a crystalline material. In this paper, carbon nitride materials prepared by two different techniques are analysed, and found to be remarkably similar in bonding and structure. The materials appear to have a primarily sp{sup 2} bonded carbon structure with a lower bond length than found in an amorphous carbon. This is explained by nitrogen substituting into `rings` to a saturation level of about one nitrogen per three carbon atoms. No evidence was found for a crystalline structure of formula C{sub 3}N{sub 4}, or any amorphous derivative of it. 16 refs., 1 tab., 5 figs.

  9. Nitrogen-doped porous carbon derived from biomass waste for high-performance supercapacitor.

    Science.gov (United States)

    Ma, Guofu; Yang, Qian; Sun, Kanjun; Peng, Hui; Ran, Feitian; Zhao, Xiaolong; Lei, Ziqiang

    2015-12-01

    High capacitance property and low cost are the pivotal requirements for practical application of supercapacitor. In this paper, a low cost and high capacitance property nitrogen-doped porous carbon with high specific capacitance is prepared. The as-prepared nitrogen-doped porous carbon employing potato waste residue (PWR) as the carbon source, zinc chloride (ZnCl2) as the activating agent and melamine as nitrogen doping agent. The morphology and structure of the carbon materials are studied by scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray diffraction (XRD) and Raman spectra. The surface area of the nitrogen-doped carbon which prepared under 700°C is found to be 1052m(2)/g, and the specific capacitance as high as 255Fg(-1) in 2M KOH electrolyte is obtained utilize the carbon as electrode materials. The electrode materials also show excellent cyclability with 93.7% coulombic efficiency at 5Ag(-1) current density of for 5000cycles.

  10. Enhanced tunnel transport in disordered carbon superlattice structures incorporated with nitrogen

    Science.gov (United States)

    Katkov, Mikhail V.; Bhattacharyya, Somnath

    2012-06-01

    The possibility for enhanced tunnel transport through the incorporation of nitrogen in a quasi-one dimensional superlattice structure of amorphous carbon (a -C) made of sp2-C and sp3-C rich phases is shown by using a tight-binding model. The proposed superstructure can be described by a set of disordered graphite-like carbon clusters (acting as quantum wells) separated by a thin layer of diamond-like carbon (barriers) where the variation of the width and depth of the carbon clusters significantly control the electron transmission peaks. A large structural disorder in the pure carbon system, introduced through the variation of the bond length and associated deformation potential for respective carbon phases, was found to suppress the sharp features of the transmission coefficients. A small percentage of nitrogen addition to the carbon clusters can produce a distinct transmission peak at the low energy; however, it can be practically destroyed due to increase of the level of disorder of carbon sites. Whereas pronounced resonance peaks, both for C and N sites can be achieved through controlling the arrangement of the nitrogen sites of increased concentration within the disordered sp2-C clusters. The interplay of disorder associated with N and C sites illustrated the tunable nature of resistance of the structures as well as their characteristic times.

  11. The Effect of Compaction on Urease Enzyme Activity, Carbon Dioxide Evaluation and Nitrogen Mineralisation

    OpenAIRE

    Ayten KARACA; Abdullah BARAN; KAKTANIR, Koray

    2000-01-01

    The effects of compaction on urease enzyme activity, carbon dioxide evaluation and nitrogen mineralisation of urea-treated and untreated soils were investigated. Soils were compacted at compaction levels of O kgcm -2 , 2 kgcm -2 and 4 kgcm -2 and incubated for 28 days. The changes in urease enzyme activity, CO 2 evaluation and nitrogen mineralization were determined during incubation periods. Urease enzyme activity was decreased significantly (P

  12. Enhancing nitrogen removal from low carbon to nitrogen ratio wastewater by using a novel sequencing batch biofilm reactor.

    Science.gov (United States)

    Zou, Jinte; Li, Jun; Ni, Yongjiong; Wei, Su

    2016-12-01

    Removing nitrogen from wastewater with low chemical oxygen demand/total nitrogen (COD/TN) ratio is a difficult task due to the insufficient carbon source available for denitrification. Therefore, in the present work, a novel sequencing batch biofilm reactor (NSBBR) was developed to enhance the nitrogen removal from wastewater with low COD/TN ratio. The NSBBR was divided into two units separated by a vertical clapboard. Alternate feeding and aeration was performed in the two units, which created an anoxic unit with rich substrate content and an aeration unit deficient in substrate simultaneously. Therefore, the utilization of the influent carbon source for denitrification was increased, leading to higher TN removal compared to conventional SBBR (CSBBR) operation. The results show that the CSBBR removed up to 76.8%, 44.5% and 10.4% of TN, respectively, at three tested COD/TN ratios (9.0, 4.8 and 2.5). In contrast, the TN removal of the NSBBR could reach 81.9%, 60.5% and 26.6%, respectively, at the corresponding COD/TN ratios. Therefore, better TN removal performance could be achieved in the NSBBR, especially at low COD/TN ratios (4.8 and 2.5). Furthermore, it is easy to upgrade a CSBBR into an NSBBR in practice.

  13. The reactivity of lattice carbon and nitrogen species in molybdenum (oxy)carbonitrides prepared by single-source routes

    Energy Technology Data Exchange (ETDEWEB)

    AlShalwi, M. [WestCHEM, School of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Hargreaves, J.S.J., E-mail: Justin.Hargreaves@glasgow.ac.uk [WestCHEM, School of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Liggat, J.J.; Todd, D. [WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL (United Kingdom)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Molybdenum (oxy)carbonitrides have been prepared from single source routes. Black-Right-Pointing-Pointer Nitrogen species are more reactive than carbon species within the carbonitrides. Black-Right-Pointing-Pointer The reactivity of nitrogen species is a function of carbonitride composition. -- Abstract: Molybdenum (oxy)carbonitrides of different compositions have been prepared from hexamethylenetetramine molybdate and ethylenediamine molybdate precursors and the reactivity of the lattice carbon and nitrogen species within them has been determined by temperature programmed reduction and thermal volatilisation studies. Nitrogen is found to be much more reactive than carbon and the nature of its reactivity is influenced by composition with the presence of carbon enhancing the reactivity of nitrogen. The difference in reactivity observed indicates that molybdenum carbonitrides are not suitable candidates as reagents for which the simultaneous loss of nitrogen and carbon from the lattice would be desirable.

  14. Revealing the Origin of Activity in Nitrogen-Doped Nanocarbons towards Electrocatalytic Reduction of Carbon Dioxide

    DEFF Research Database (Denmark)

    Xu, Junyuan; Kan, Yuhe; Huang, Rui;

    2016-01-01

    Carbon nanotubes (CNTs) are functionalized with nitrogen atoms for reduction of carbon dioxide (CO2). The investigation explores the origin of the catalyst’s activity and the role of nitrogen chemical states therein. The catalysts show excellent performances, with about 90% current efficiency...... for CO formation and stability over 60 hours. The Tafel analyses and density functional theory calculations suggest that the reduction of CO2 proceeds through an initial rate-determining transfer of one electron to CO2, which leads to the formation of carbon dioxide radical anion (CO2C). The initial...... reduction barrier is too high on pristine CNTs, resulting in a very high overpotentials at which the hydrogen evolution reaction dominates over CO2 reduction.The doped nitrogen atoms stabilize the radical anion,thereby lowering the initial reduction barrier and improving the intrinsic activity. The most...

  15. Nitrogen-Doped Carbon Nanotube and Graphene Materials for Oxygen Reduction Reactions

    Directory of Open Access Journals (Sweden)

    Qiliang Wei

    2015-09-01

    Full Text Available Nitrogen-doped carbon materials, including nitrogen-doped carbon nanotubes (NCNTs and nitrogen-doped graphene (NG, have attracted increasing attention for oxygen reduction reaction (ORR in metal-air batteries and fuel cell applications, due to their optimal properties including excellent electronic conductivity, 4e− transfer and superb mechanical properties. Here, the recent progress of NCNTs- and NG-based catalysts for ORR is reviewed. Firstly, the general preparation routes of these two N-doped carbon-allotropes are introduced briefly, and then a special emphasis is placed on the developments of both NCNTs and NG as promising metal-free catalysts and/or catalyst support materials for ORR. All these efficient ORR electrocatalysts feature a low cost, high durability and excellent performance, and are thus the key factors in accelerating the widespread commercialization of metal-air battery and fuel cell technologies.

  16. Determination of organic milk authenticity using carbon and nitrogen natural isotopes.

    Science.gov (United States)

    Chung, Ill-Min; Park, Inmyoung; Yoon, Jae-Yeon; Yang, Ye-Seul; Kim, Seung-Hyun

    2014-10-01

    Natural stable isotopes of carbon and nitrogen ((12)C, (13)C, (14)N, (15)N) have abundances unique to each living creature. Therefore, measurement of the stable isotope ratio of carbon and nitrogen (δ(13)C=(13)C/(12)C, δ(15)N=(15)N/(14)N) in milk provides a reliable method to determine organic milk (OM) authenticity. In the present study, the mean δ(13)C value of OM was higher than that of conventional milk (CM), whereas the mean δ(15)N value of OM was lower than that of CM; nonetheless both δ(13)C and δ(15)N values were statistically different for the OM and CM (Pauthenticity using stable isotopes of carbon and nitrogen.

  17. Carbon and Nitrogen Isotope Systematics in a Sector-Zoned Diamond from the Mir Kimberlite, Yakutia

    Science.gov (United States)

    Hauri, E.; Bulanova, G.; Pearson, G.; Griffin, B.

    2002-05-01

    A single Yakutian octahedral diamond, displaying striking cubic and octahedral growth sectors surrounded by an octahedral rim, has been analysed for carbon and nitrogen isotopic compositions by SIMS and for nitrogen concentration (by SIMS and FTIR) and nitrogen aggregation state (FTIR). A graphite "seed" inclusion identified within the diamond, enriched in K, Ca, Ti, Rb and Sr, provides evidence that the diamond may have grown from a carbonate melt/fluid interacting with upper mantle rocks. Carbon and nitrogen isotope compositions become progressively heavier from the core region (d13C = -7 to -5 and d15N= -3) towards the inner rim zones (d13C = -3 and d15N = +8.9 to +5) of the diamond. Nitrogen concentration and aggregation measurements show corresponding decreases that generally correlate with the isotopic variations. These systematic variations within the core and intermediate regions of the diamond are consistent with their formation during diamond growth from CO2-rich fluids as a continuous event, accompanied by slight progressive isotopic fractionation of carbon and nitrogen. However, the observed isotope and nitrogen abundance trends are not those predicted from thermodynamic modelling of fluid-solid equilibria in a C-N-O-H-bearing system due to changes in parameters such as fO2 (Deines, 1980; Deines et al 1989). Within the finely-zoned octahedral rim region, non-systematic variations in nitrogen abundance, nitrogen aggregation, and nitrogen and carbon isotope ratios were observed. Several interpretations are given for this phenomenon, including kinetic effects during growth of the diamond rim under different conditions from those of the core-intermediate regions, or rapidly changing fluid sources during the growth. No fractionation of nitrogen isotopes between cubic and octahedral growth zones was identified within the studied diamond, in contrast with the fractionation phenomena found in synthetic diamonds of mixed growth. Our results illustrate the

  18. Amorphous Hydrogenated Carbon-Nitrogen Alloy Thin Films for Solar Cell Application

    Institute of Scientific and Technical Information of China (English)

    ZHOU Zhi-Bin; DING Zheng-Ming; PANG Qian-Jun; CUI Rong-Qiang

    2001-01-01

    Amorphous hydrogenated carbon-nitrogen alloy (a-CNx :H) thin films have been deposited on silicon substratesby improved dc magnetron sputtering from a graphite target in nitrogen and hydrogen gas discharging. Thefilms are investigated by using Raman spectroscopy, x-ray photoelectron spectroscopy, spectral ellipsometer and electron spin resonance techniques. The optimized process condition for solar cell application is discussed. Thephotovoltaic property of a-CNx:H/silicon heterojunctions can be improved by the adjustment of the pressureratio of hydrogen to nitrogen and unbalanced magnetic field intensity. Open-circuit voltage and short-circuitcurrent reach 300mV and 5.52 Ma/cm2, respectively.

  19. Nitrogen-doped porous carbon with an ultrahigh specific surface area for superior performance supercapacitors

    Science.gov (United States)

    Long, Chao; Zhuang, Jianle; Xiao, Yong; Zheng, Mingtao; Hu, Hang; Dong, Hanwu; Lei, Bingfu; Zhang, Haoran; Liu, Yingliang

    2016-04-01

    Owing to its abundant nitrogen content, silk cocoon is a promising precursor for the synthesis of Nitrogen-doped porous carbon (N-PC). Using a simple staged KOH activation, the prepared sample displays particular nanostructure with ultrahigh specific surface area (3841 m2 g-1) and appropriate pore size, providing favorable pathways for transportation and penetration of electrolyte ions. Additionally, the doped nitrogen atoms ensure the samples with pseudocapacitive behavior. Those special characteristics endow N-PCs with high capacity, low resistance, and long-term stability, indicating a wonderful potential for application in energy-storage devices.

  20. Benthic biogeochemical cycling, nutrient stoichiometry, and carbon and nitrogen mass balances in a eutrophic freshwater bay

    Science.gov (United States)

    Klump, J.V.; Fitzgerald, S.A.; Waplesa, J.T.

    2009-01-01

    Green Bay, while representing only ,7% of the surface area and ??1.4% of the volume of Lake Michigan, contains one-third of the watershed of the lake, and receives approximately one-third of the total nutrient loading to the Lake Michigan basin, largely from the Fox River at the southern end of the bay. With a history of eutrophic conditions dating back nearly a century, the southern portion of the bay behaves as an efficient nutrient and sediment trap, sequestering much of the annual carbon and nitrogen input within sediments accumulating at up to 1 cm per year. Depositional fluxes of organic matter varied from ??0.1 mol C m-2 yr-1 to >10 mol C m-2 yr-1 and were both fairly uniform in stoichiometric composition and relatively labile. Estimates of benthic recycling derived from pore-water concentration gradients, whole-sediment incubation experiments, and deposition-burial models of early diagenesis yielded an estimated 40% of the carbon and 50% of the nitrogen recycled back into the overlying water. Remineralization was relatively rapid with ??50% of the carbon remineralized within <15 yr of deposition, and a mean residence time for metabolizable carbon and nitrogen in the sediments of 20 yr. On average, organic carbon regeneration occurred as 75% CO2, 15% CH4, and 10% dissolved organic carbon (DOC). Carbon and nitrogen budgets for the southern bay were based upon direct measurements of inputs and burial and upon estimates of export and production derived stoichiometrically from a coupled phosphorus budget. Loadings of organic carbon from rivers were ??3.7 mol m-2 yr-1, 80% in the form of DOC and 20% as particulate organic carbon. These inputs were lost through export to northern Green Bay and Lake Michigan (39%), through sediment burial (26%), and net CO2 release to the atmosphere (35%). Total carbon input, including new production, was 4.54 mol m-2 C yr-1, equivalent to ??10% of the gross annual primary production. Nitrogen budget terms were less well quantified

  1. [Assessment on the availability of nitrogen fertilization in improving carbon sequestration potential of China's cropland soil].

    Science.gov (United States)

    Lu, Fei; Wang, Xiao-Ke; Han, Bing; Ouyang, Zhi-Yun; Duan, Xiao-Nan; Zheng, Hua

    2008-10-01

    With reference to the situation of nitrogen fertilization in 2003 and the recommendations from agricultural experts on fertilization to different crops, two scenarios, namely, 'current situation' and 'fertilization as recommended', were set for estimating the current and potential carbon sequestration of China's cropland soil under nitrogen fertilization. After collecting and analyzing the typical data from the long-term agricultural experiment stations all over China, and based on the recent studies of soil organic matter and nutrient dynamics, we plotted China into four agricultural regions, and estimated the carbon sequestration rate and potential of cropland soil under the two scenarios in each province of China. Meanwhile, with the data concerning fossil fuel consumption for fertilizer production and nitrogen fertilization, the greenhouse gas leakage caused by nitrogen fertilizer production and application was estimated with the help of the parameters given by domestic studies and IPCC. We further proposed that the available carbon sequestration potential of cropland soil could be taken as the criterion of the validity and availability of carbon sequestration measures. The results showed that the application of synthetic nitrogen fertilizer could bring about a carbon sequestration potential of 21.9 Tg C x a(-1) in current situation, and 30.2 Tg C x a(-1) with fertilization as recommended. However, under the two scenarios, the greenhouse gas leakage caused by fertilizer production and application would reach 72.9 Tg C x a(-1) and 91.4 Tg C x a(-1), and thus, the actual available carbon sequestration potential would be -51.0 Tg C x a(-1) and -61.1 Tg C x a(-1), respectively. The situation was even worse under the 'fertilization as recommended' scenario, because the increase in the amount of nitrogen fertilization would lead to 10. 1 Tg C x a(-1) or more net greenhouse gas emission. All these results indicated that the application of synthetic nitrogen fertilizer

  2. Carbon and nitrogen mineralization are decoupled in organo-mineral fractions

    Science.gov (United States)

    Bimüller, Carolin; Mueller, Carsten W.; von Lützow, Margit; Kreyling, Olivia; Kölbl, Angelika; Haug, Stephan; Schloter, Michael; Kögel-Knabner, Ingrid

    2015-04-01

    To improve our comprehension how carbon and nitrogen mineralization are linked in soils, we used a controlled laboratory mineralization approach and compared carbon and nitrogen dynamics in the bulk soil and in soil fractions. Topsoil of a Rendzic Leptosol from a beech forest site near Tuttlingen, Germany, was fractionated into three particle size classes: sand (2000 to 20 µm), silt (20 to 2 µm), and clay (nitrogen mineralization dynamics, and assessed carbon respiration as well as nitrogen mineralization and microbial biomass carbon and nitrogen contents. Soil organic matter in the incubated fractions was considered by a subsequent density fractionation. The chemical composition of selected samples was qualitatively evaluated by 13C-NMR spectroscopy. When summing up the mineralization rates of the single fractions, the values for respired carbon equaled the bulk soil, whereas the mathematical recombination of mineral nitrogen in all fractions was significantly less than in bulk soil. Hence, carbon mineralization was not affected by the damage of the aggregated soil structure via fractionation, whereas nitrogen mineralization was reduced. Fractionation increased the surface area providing accessory mineral surfaces, which allowed new binding of especially nitrogen-rich compounds, besides ammonium fixation via cation exchange. Density fractionation revealed that organic matter in the sand fraction contained mainly particulate organic matter present as light material comprising partly decomposed plant remnants. The organic matter in the clay fraction was mostly adsorbed on mineral surfaces. Organic matter in the sand and in the clay fraction was dominated by O/N-alkyl C indicating low recalcitrance, but the C/N ratio of organic matter narrowed with decreasing particle size. These results also imply that the C/N ratio as well as the alkyl C to O/N-alkyl C ratio are not suitable to draw conclusions regarding biological decomposability of plant residues when

  3. The Effect of Different Nitrogen Form on Key Enzyme Activity of Sugarbeet (Vulgaris L.) Carbon and Nitrogen Metabolism

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This article analyses the effect of the proportion of the different nitrogen forms on key enzyme activity of carbon and nitrogen metabolism under the condition of nutritional water while Tian Yan-7 was used as experimental material. The result showed that nitrate reductase(NR) activity in the leaves gradually enhanced with the increase of NO-3. No matter in root or leaves ,glutamina synthetase (GS) activity first enhanced with increasing NH4+ when NH4+ was lower than that of NO-3 ,and GS activity was the highest when NH4+and NO3-was equal ,then GS activity declined with NH4+ increasing further. In the anaphase of growth ,synthetic activity in root of sucrose synthetase(SS) in the mixed NH4+ and NO3- was obviously highr than or NO3- alone. Both of the root and sugar yields were the highest when the proportion of NH4+ and NO3- was 1: 1.

  4. Quantum Chemistry Calculation on Oxygen and Nitrogen Adsorption in Carbon Nanotude

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Oxygen and nitrogen adsorption in single-walled carbon nanotube (SWCNT) is studied by density function and discrete variational (DFT-DVM) method.The models of O2 and N2 adsorption in the SWCNT are optimized based on the energy minimization.The calculated results of density of state,populations and energy gaps of the molecular orbitals show that oxygen adsorption in SWCNT increases the carbon nanotube`s electrical conductivity more notably than nitrogen adsorption,which is consistent with the experiment.

  5. Nitrogen, Phosphorus and Carbon Excretion and Losses in Growing Pigs Fed Danish or Asian Diets

    DEFF Research Database (Denmark)

    Prapaspongsa, Trakarn; Vu, T K V; Poulsen, Hanne Damgaard

    2008-01-01

    The objectives of this study were to determine inputs and outputs of nitrogen (N), phosphorus (P) and carbon (C) and to estimate the nutrient losses during housing and storage in order to address these important parts of the whole manure management systems in pigs fed different diets.......The objectives of this study were to determine inputs and outputs of nitrogen (N), phosphorus (P) and carbon (C) and to estimate the nutrient losses during housing and storage in order to address these important parts of the whole manure management systems in pigs fed different diets....

  6. [Dynamics of carbon and nitrogen storage of Cupressus chengiana plantations in the arid valley of Minjiang River, Southwest China].

    Science.gov (United States)

    Luo, Da; Feng, Qiu-hong; Shi, Zuo-min; Li, Dong-sheng; Yang, Chang-xu; Liu, Qian-li; He, Jian-she

    2015-04-01

    The carbon and nitrogen storage and distribution patterns of Cupressus chengiana plantation ecosystems with different stand ages in the arid valley of Minjiang River were studied. The results showed that carbon contents in different organs of C. chengiana were relatively stable, while nitrogen contents were closely related to different organs, and soil organic carbon and nitrogen contents increased with the stand age. Carbon and nitrogen storage in vegetation layer, soil layer, and the whole ecosystem of the plantation increased with the stand age. The values of total carbon storage in the 13-, 11-, 8-, 6- and 4-year-old C. chengiana plantation ecosystems were 190.90, 165.91, 144.57, 119.44, and 113.49 t x hm(-2), and the values of total nitrogen storage were 19.09, 17.97, 13.82, 13.42, and 12.26 t x hm(-2), respectively. Most of carbon and nitrogen were stored in the 0-60 cm soil layer in the plantation ecosystems and occupied 92.8% and 98.8%, respectively, and the amounts of carbon and nitrogen stored in the top 0-20 cm soil layer, accounted for 54.4% and 48.9% of those in the 0-60 cm soil layer, respectively. Difference in distribution of carbon and nitrogen storage was observed in the vegetation layer. The percentage of carbon storage in tree layer (3.7%) were higher than that in understory vegetation (3.5%), while the percentage of nitrogen storage in tree layer (0.5%) was lower than that in understory (0.7%). The carbon and nitrogen storage and distribution patterns in the plantations varied obviously with the stand age, and the plantation ecosystems at these age stages could accumulate organic carbon and nitrogen continuously.

  7. Carbon and Nitrogen dynamics in forest soils depending on light conditions and tree species

    Science.gov (United States)

    Veselinovic, Bojana; Hager, Herbert

    2013-04-01

    Climate change mitigation actions under the Kyoto Protocol apply among other decreases of CO2-emissions and/or increases of carbon (C) stocks. As soils represent the second biggest C-reservoir on Earth, an exact estimation of the stocks and reliable knowledge on C-dynamics in forest soils is of high importance. Anyhow, here, the accurate GHG-accounting, emission reductions and increase in C stocks is hampered due to lack of reliable data and solid statistical methods for the factors which influence C-sequestration in and its release from these systems. In spite of good progress in the scientific research, these factors are numerous and diverse in their interactions. This work focuses on influence of the economically relevant tree species - Picea abies, Fagus sylvatica and Quercus spp. - and light conditions on forest floor and mineral soil C and N dynamics in forest soils. Spruce monocultures have been widely used management practices in central European forests during the past century. Such stands are in lower altitudes and on heavy and water logged soils unstable and prone to disturbances, especially to windthrows. We hypothesize that windthrow areas loose C & N and that the establishment of the previous nutrient stocks is, if at all, only possible to be reached over the longer periods of time. We research also how the increased OM depletion affects the change of C & N stocks in forest floor vs. mineral soil. Conversion of such secondary spruce monocultures to site adequate beech and oak forests may enable higher stocks allocated predominantly as stable organic carbon and as plant available nitrogen. For this purpose sites at 300-700 m altitude with planosols were chosen in the region of the Northern Alpine Foothills. A false chronosequence approach was used in order to evaluate the impacts of the tree species and change in light conditions on dynamic of C & N in the forest floor and mineral soil, over the period 0-100 (for oak 120 y.) years. The C- and N

  8. Nanostructured nitrogen-doped mesoporous carbon derived from polyacrylonitrile for advanced lithium sulfur batteries

    Science.gov (United States)

    Liu, Ying; Zhao, Xiaohui; Chauhan, Ghanshyam S.; Ahn, Jou-Hyeon

    2016-09-01

    Nitrogen doping in carbon matrix can effectively improve the wettability of electrolyte and increase electric conductivity of carbon by ensuring fast transfer of ions. We synthesized a series of nitrogen-doped mesoporous carbons (CPANs) via in situ polymerization of polyacrylonitrile (PAN) in SBA-15 template followed by carbonization at different temperatures. Carbonization results in the formation of ladder structure which enhances the stability of the matrix. In this study, CPAN-800, carbon matrix synthesized by the carbonization at 800 °C, was found to possess many desirable properties such as high specific surface area and pore volume, moderate nitrogen content, and highly ordered mesoporous structure. Therefore, it was used to prepare S/CPAN-800 composite as cathode material in lithium sulfur (Li-S) batteries. The S/CPAN-800 composite was proved to be an excellent material for Li-S cells which delivered a high initial discharge capacity of 1585 mAh g-1 and enhanced capacity retention of 862 mAh g-1 at 0.1 C after 100 cycles.

  9. Thermal acclimation of leaf respiration of tropical trees and lianas: response to experimental canopy warming, and consequences for tropical forest carbon balance.

    Science.gov (United States)

    Slot, Martijn; Rey-Sánchez, Camilo; Gerber, Stefan; Lichstein, Jeremy W; Winter, Klaus; Kitajima, Kaoru

    2014-09-01

    Climate warming is expected to increase respiration rates of tropical forest trees and lianas, which may negatively affect the carbon balance of tropical forests. Thermal acclimation could mitigate the expected respiration increase, but the thermal acclimation potential of tropical forests remains largely unknown. In a tropical forest in Panama, we experimentally increased nighttime temperatures of upper canopy leaves of three tree and two liana species by on average 3 °C for 1 week, and quantified temperature responses of leaf dark respiration. Respiration at 25 °C (R25 ) decreased with increasing leaf temperature, but acclimation did not result in perfect homeostasis of respiration across temperatures. In contrast, Q10 of treatment and control leaves exhibited similarly high values (range 2.5-3.0) without evidence of acclimation. The decrease in R25 was not caused by respiratory substrate depletion, as warming did not reduce leaf carbohydrate concentration. To evaluate the wider implications of our experimental results, we simulated the carbon cycle of tropical latitudes (24°S-24°N) from 2000 to 2100 using a dynamic global vegetation model (LM3VN) modified to account for acclimation. Acclimation reduced the degree to which respiration increases with climate warming in the model relative to a no-acclimation scenario, leading to 21% greater increase in net primary productivity and 18% greater increase in biomass carbon storage over the 21st century. We conclude that leaf respiration of tropical forest plants can acclimate to nighttime warming, thereby reducing the magnitude of the positive feedback between climate change and the carbon cycle.

  10. Ground-Based Lidar Measurements of Forest Canopy Structure as Predictors of Net Primary Production Across Successional Time

    Science.gov (United States)

    Scheuermann, C. M.; Gough, C. M.; Nave, L. E.

    2015-12-01

    Forest canopy structure is a key predictor of gas exchange processes that control carbon (C) uptake, including the allocation of photosynthetically fixed C to new plant biomass growth, or net primary production (NPP). Prior work suggests forest canopy structural complexity (CSC), the arrangement of leaves within a volume of canopy, changes as forests develop and is a strong predictor of NPP. However, the expressions of CSC that best predict NPP over decadal to century timescales is unknown. Our objectives were to use multiple remote sensing observations to characterize forest canopy structure in increasing dimensional complexity over a forest age gradient, and to identify which expressions of physical structure best served as proxies of NPP. The study at the University of Michigan Biological Station in Pellston, MI, USA uses two parallel forest chronosequences with different harvesting and fire disturbance histories and includes three old-growth ecosystems varying in canopy composition. We have derived several expressions of 2-D and 3-D forest canopy structure from hemispherical images, a ground-based portable canopy lidar (PCL), and a 3-D terrestrial lidar scanner (TLS), and are relating these structural metrics with NPP and light and nitrogen allocation within the canopy. Preliminary analysis shows that old-growth stands converged on a common mean CSC, but with substantially higher within-stand variation in complexity as deciduous tree species increased in forest canopy dominance. Forest stands that were more intensely disturbed were slower to recover leaf area index (LAI) as they regrew, but 2-D measures of CSC increased similarly as forests aged, regardless of disturbance history. Ongoing work will relate long-term trends in forest CSC with NPP and resource allocation to determine which forest structure remote sensing products are most useful for modeling and scaling C cycling processes through different stages of forest development.

  11. Biofilm Removal Using Carbon Dioxide Aerosols without Nitrogen Purge.

    Science.gov (United States)

    Hong, Seongkyeol; Jang, Jaesung

    2016-11-06

    Biofilms can cause serious concerns in many applications. Not only can they cause economic losses, but they can also present a public health hazard. Therefore, it is highly desirable to remove biofilms from surfaces. Many studies on CO2 aerosol cleaning have employed nitrogen purges to increase biofilm removal efficiency by reducing the moisture condensation generated during the cleaning. However, in this study, periodic jets of CO2 aerosols without nitrogen purges were used to remove Pseudomonas putida biofilms from polished stainless steel surfaces. CO2 aerosols are mixtures of solid and gaseous CO2 and are generated when high-pressure CO2 gas is adiabatically expanded through a nozzle. These high-speed aerosols were applied to a biofilm that had been grown for 24 hr. The removal efficiency ranged from 90.36% to 98.29% and was evaluated by measuring the fluorescence intensity of the biofilm as the treatment time was varied from 16 sec to 88 sec. We also performed experiments to compare the removal efficiencies with and without nitrogen purges; the measured biofilm removal efficiencies were not significantly different from each other (t-test, p > 0.55). Therefore, this technique can be used to clean various bio-contaminated surfaces within one minute.

  12. Utilization of recovered nitrogen from hydrothermal carbonization process by Arthrospira platensis.

    Science.gov (United States)

    Yao, Changhong; Pan, Yanfei; Lu, Hongbin; Wu, Peichun; Meng, Yingying; Cao, Xupeng; Xue, Song

    2016-07-01

    In the context of sustainable cultivation of microalgae, the present study focused on the use of nitrogen from the hot-water extracted biomass residue of Arthrospira platensis by hydrothermal carbonization (HTC) and the sequential cultivation of the same alga with the HTC aqueous phase (AP). Nearly 90% of the nitrogen recovered from HTC into AP was in the organic form. Under nitrogen-limited condition with HTCAP as nitrogen source the yield and content of carbohydrate were enhanced by 21% and 15% respectively compared with that under the same nitrogen level provided by NaNO3, which entitled HTCAP for the substitution of conventional nitrate. In the same way pilot-scale cultivation of A. platensis in raceway ponds outdoors demonstrated that carbohydrate content of 43.8% DW and productivity of 10.3g/m(2)/d was achieved. Notably 54% of organic nitrogen in the HTCAP could be recycled by cultivation of pre-nitrogen starved A. platensis as seeds under nitrogen limitation.

  13. Physiology and gene expression profiles of Dekkera bruxellensis in response to carbon and nitrogen availability.

    Science.gov (United States)

    de Barros Pita, Will; Silva, Denise Castro; Simões, Diogo Ardaillon; Passoth, Volkmar; de Morais, Marcos Antonio

    2013-11-01

    The assimilation of nitrate, a nitrogenous compound, was previously described as an important factor favoring Dekkera bruxellensis in the competition with Saccharomyces cerevisiae for the industrial sugarcane substrate. In this substrate, nitrogen sources are limited and diverse, and a recent report showed that amino acids enable D. bruxellensis to grow anaerobically. Thus, understanding the regulation of nitrogen metabolism is one fundamental aspect to comprehend the competiveness of D. bruxellensis in the fermentation environment. In the present study, we evaluated the physiological and transcriptional profiles of D. bruxellensis in response to different carbon and nitrogen supplies to determine their influence on growth, sugar consumption, and ethanol production. Besides, the expression of genes coding for nitrogen permeases and enzymes involved in the biosynthesis of glutamate and energetic metabolism were investigated under these conditions. Our data revealed that genes related to nitrogen uptake in D. bruxellensis are under the control of nitrogen catabolite repression. Moreover, we provide indications that glutamate dehydrogenase and glutamate synthase may switch roles as the major pathway for glutamate biosynthesis in D. bruxellensis. Finally, our data showed that in nonoptimal growth conditions, D. bruxellensis leans toward the respiratory metabolism. The results presented herein show that D. bruxellensis and S. cerevisiae share similar regulation of GDH–GOGAT pathway, while D. bruxellensis converts less glucose to ethanol than S. cerevisiae do when nitrogen is limited. The consequence of this particularity to the industrial process is discussed.

  14. A Natural Light/Dark Cycle Regulation of Carbon-Nitrogen Metabolism and Gene Expression in Rice Shoots.

    Science.gov (United States)

    Li, Haixing; Liang, Zhijun; Ding, Guangda; Shi, Lei; Xu, Fangsen; Cai, Hongmei

    2016-01-01

    Light and temperature are two particularly important environmental cues for plant survival. Carbon and nitrogen are two essential macronutrients required for plant growth and development, and cellular carbon and nitrogen metabolism must be tightly coordinated. In order to understand how the natural light/dark cycle regulates carbon and nitrogen metabolism in rice plants, we analyzed the photosynthesis, key carbon-nitrogen metabolites, and enzyme activities, and differentially expressed genes and miRNAs involved in the carbon and nitrogen metabolic pathway in rice shoots at the following times: 2:00, 6:00, 10:00, 14:00, 18:00, and 22:00. Our results indicated that more CO2 was fixed into carbohydrates by a high net photosynthetic rate, respiratory rate, and stomatal conductance in the daytime. Although high levels of the nitrate reductase activity, free ammonium and carbohydrates were exhibited in the daytime, the protein synthesis was not significantly facilitated by the light and temperature. In mRNA sequencing, the carbon and nitrogen metabolism-related differentially expressed genes were obtained, which could be divided into eight groups: photosynthesis, TCA cycle, sugar transport, sugar metabolism, nitrogen transport, nitrogen reduction, amino acid metabolism, and nitrogen regulation. Additionally, a total of 78,306 alternative splicing events have been identified, which primarily belong to alternative 5' donor sites, alternative 3' acceptor sites, intron retention, and exon skipping. In sRNA sequencing, four carbon and nitrogen metabolism-related miRNAs (osa-miR1440b, osa-miR2876-5p, osa-miR1877 and osa-miR5799) were determined to be regulated by natural light/dark cycle. The expression level analysis showed that the four carbon and nitrogen metabolism-related miRNAs negatively regulated their target genes. These results may provide a good strategy to study how natural light/dark cycle regulates carbon and nitrogen metabolism to ensure plant growth and

  15. Biosynthetic origin of the carbon skeleton and nitrogen atom of pamamycin-607, a nitrogen-containing polyketide.

    Science.gov (United States)

    Hashimoto, Makoto; Komatsu, Haruhiko; Kozone, Ikuko; Kawaide, Hiroshi; Abe, Hiroshi; Natsume, Masahiro

    2005-02-01

    The biosynthesis of pamamycin-607 (PM-607), a sixteen-membered macrodiolide compound, was studied with 13C- and 15N-labeled precursor units in Streptomyces alboniger. Feeding experiments with 13C-labeled acetate or propionate indicate that the carbon skeleton of PM-607 was derived from six acetate, four propionate and three succinate units. MS analyses of 15N-labeled PM-607 suggest that the nitrogen atom in PM-607 was derived from the alpha-amino group of an amino acid.

  16. Carbon and carbon dioxide accumulation by marandu grass under nitrogen fertilization and irrigation

    Directory of Open Access Journals (Sweden)

    Elisângela Dupas

    2016-06-01

    Full Text Available ABSTRACT Nitrogen (N is the most limiting nutrient for growth of forage grasses, especially in conditions of low water availability. Therefore, it is important to evaluate the effect of N fertilization and irrigation on the accumulation of carbon (C and carbon dioxide (CO2 by marandu grass in the Cerrado Paulista, in the rainy and dry seasons. Experiments were conducted to evaluate N fertilization in each season, with and without irrigation. Five N rates were used (0, 50, 100, 150 and 200 kg ha-1 per cutting, using urea as N source, totaling 0, 300, 600, 900 and 1200 kg ha-1 in the rainy season and 0, 100, 200, 300 and 400 kg ha-1 in the dry season. The experiments were arranged in a split-plot randomized block design. There was no significant interaction (p > 0.05 between N and time of fertilization in the irrigated experiment. However, N promoted a quadratic effect in organic matter production (OMP, accumulation of C and CO2 by marandu grass, while there was no influence of the seasons. In the non-irrigated experiment, the interaction between N rates and seasons was significant (p < 0.05 only for the rainy season. Organic matter production and C and CO2 accumulation was greater in the rainy season than in the dry season. Irrigation provided increases of approximately 20% in C and CO2 accumulation. The use of N and irrigation increases the accumulation of C and CO2 by marandu grass, and this increase is higher during the rainy season.

  17. Carbon sequestration and Jerusalem artichoke biomass under nitrogen applications in coastal saline zone in the northern region of Jiangsu, China.

    Science.gov (United States)

    Niu, Li; Manxia, Chen; Xiumei, Gao; Xiaohua, Long; Hongbo, Shao; Zhaopu, Liu; Zed, Rengel

    2016-10-15

    Agriculture is an important source of greenhouse gases, but can also be a significant sink. Nitrogen fertilization is effective in increasing agricultural production and carbon storage. We explored the effects of different rates of nitrogen fertilization on biomass, carbon density, and carbon sequestration in fields under the cultivation of Jerusalem artichoke as well as in soil in a coastal saline zone for two years. Five nitrogen fertilization rates were tested (in guream(-2)): 4 (N1), 8 (N2), 12 (N3), 16 (N4), and 0 (control, CK). The biomass of different organs of Jerusalem artichoke during the growth cycle was significantly higher in N2 than the other treatments. Under different nitrogen treatments, carbon density in organs of Jerusalem artichoke ranged from 336 to 419gCkg(-1). Carbon sequestration in Jerusalem artichoke was higher in treatments with nitrogen fertilization compared to the CK treatment. The highest carbon sequestration was found in the N2 treatment. Soil carbon content was higher in the 0-10cm than 10-20cm layer, with nitrogen fertilization increasing carbon content in both soil layers. The highest soil carbon sequestration was measured in the N2 treatment. Carbon sequestration in both soil and Jerusalem artichoke residue was increased by nitrogen fertilization depending on the rates in the coastal saline zone studied.

  18. Endohedral nitrogen storage in carbon fullerene structures: Physisorption to chemisorption transition with increasing gas pressure

    Science.gov (United States)

    Barajas-Barraza, R. E.; Guirado-López, R. A.

    2009-06-01

    We present extensive pseudopotential density functional theory (DFT) calculations in order to analyze the structural properties and chemical reactivity of nitrogen molecules confined in spheroidal (C82) and tubelike (C110) carbon fullerene structures. For a small number of encapsulated nitrogens, the N2 species exist in a nonbonded state within the cavities and form well defined molecular conformations such as linear chains, zigzag arrays, as well as both spheroidal and tubular configurations. However, with increasing the number of stored molecules, the interaction among the confined nitrogens as well as between the N2 species and the fullerene wall is not always mainly repulsive. Actually, at high densities of the encapsulated gas, we found both adsorption of N2 to the inner carbon surface together with the formation of (N2)m molecular clusters. Total energy DFT calculations reveal that the shape of the interaction potential of a test molecule moving within the carbon cavities strongly varies with the number and proximity of the coadsorbed N2 from being purely repulsive to having short-range attractive contributions close to the inner wall. In particular, the latter are always found when a group of closely spaced nitrogens is located near the carbon cage (a fact that will naturally occur at high densities of the encapsulated gas), inducing the formation of covalent bonds between the N2 and the fullerene network. Interestingly, in some cases, the previous nitrogen adsorption to the inner surface is reversible by reducing the gas pressure. The calculated average density of states of our considered carbon compounds reveals the appearance of well defined features that clearly reflect the occurring structural changes and modifications in the adsorption properties in the systems. Our results clearly underline the crucial role played by confinement effects on the reactivity of our endohedral compounds, define this kind of materials as nonideal nanocontainers for high

  19. Modification of diamond-like carbon films by nitrogen incorporation via plasma immersion ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Flege, S., E-mail: flege@ca.tu-darmstadt.de [Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); Hatada, R.; Hoefling, M.; Hanauer, A.; Abel, A. [Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); Baba, K. [Industrial Technology Center of Nagasaki, Applied Technology Division, Omura, Nagasaki 856-0026 (Japan); Ensinger, W. [Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany)

    2015-12-15

    Highlights: • Nitrogen containing diamond-like carbon films were prepared by a plasma ignited by a high voltage. • Variation of preparation method (N{sub 2} implantation, N{sub 2} and C{sub 2}H{sub 4} co-deposition). • Maximum nitrogen content similar for co-deposition and implantation. • Electrical resistivity decreases for small nitrogen contents, increases again for higher contents. - Abstract: The addition of nitrogen to diamond-like carbon films affects properties such as the inner stress of the film, the conductivity, biocompatibility and wettability. The nitrogen content is limited, though, and the maximum concentration depends on the preparation method. Here, plasma immersion ion implantation was used for the deposition of the films, without the use of a separate plasma source, i.e. the plasma was generated by a high voltage applied to the samples. The plasma gas consisted of a mixture of C{sub 2}H{sub 4} and N{sub 2}, the substrates were silicon and glass. By changing the experimental parameters (high voltage, pulse length and repetition rate and gas flow ratio) layers with different N content were prepared. Additionally, some samples were prepared using a DC voltage. The nitrogen content and bonding was investigated with SIMS, AES, XPS, FTIR and Raman spectroscopy. Their influence on the electrical resistivity of the films was investigated. Depending on the preparation conditions different nitrogen contents were realized with maximum contents around 11 at.%. Those values were compared with the nitrogen concentration that can be achieved by implantation of nitrogen into a DLC film.

  20. Carbon and nitrogen flows during a bloom of the coccolithophore Emiliania huxleyi: Modelling a mesocosm experiment

    Science.gov (United States)

    Joassin, P.; Delille, B.; Soetaert, K.; Harlay, J.; Borges, A. V.; Chou, L.; Riebesell, U.; Suykens, K.; Grégoire, M.

    2011-04-01

    A dynamic model has been developed to represent biogeochemical variables and processes observed during experimental blooms of the coccolithophore Emiliania huxleyi induced in mesocosms over a period of 23 days. The model describes carbon (C), nitrogen (N), and phosphorus (P) cycling through E. huxleyi and the microbial loop, and computes pH and the partial pressure of carbon dioxide (pCO 2) from dissolved inorganic carbon (DIC) and total alkalinity (TA). The main innovations are: 1) the representation of E. huxleyi dynamics using an unbalanced growth model in carbon and nitrogen, 2) the gathering of formulations describing typical processes involved in the export of carbon such as primary production, calcification, cellular dissolved organic carbon (DOC) excretion, transparent exopolymer (TEP) formation and viral lyses, and 3) an original and validated representation of the calcification process as a function of the net primary production with a modulation by the intra-cellular N:C ratio mimicking the effect of nutrients limitation on the onset of calcification. It is shown that this new mathematical formulation of calcification provides a better representation of the dynamics of TA, DIC and calcification rates derived from experimental data compared to classicaly used formulations (e.g. function of biomass or of net primary production without any modulation term). In a first step, the model has been applied to the simulations of present pCO 2 conditions. It adequately reproduces the observations for chemical and biological variables and provides an overall view of carbon and nitrogen dynamics. Carbon and nitrogen budgets are derived from the model for the different phases of the bloom, highlighting three distinct phases, reflecting the evolution of the cellular C:N ratio and the interaction between hosts and viruses. During the first phase, inorganic nutrients are massively consumed by E. huxleyi increasing its biomass. Uptakes of carbon and nitrogen are

  1. Mesoporous Nitrogen Doped Carbon-Glass Ceramic Cathode for High Performance Lithium-Oxygen Battery

    Science.gov (United States)

    2012-06-01

    Hardwick, and J.- M. Tarascon, Nature Materials, vol. 11, pp 19-29, 2012. 2. Linden , D. (Ed), Handbook of Batteries , 2nd Edition, Mc-Graw-Hill, New...AFRL-RQ-WP-TP-2015-0053 MESOPOROUS NITROGEN DOPED CARBON-GLASS CERAMIC CATHODE FOR HIGH PERFORMANCE LITHIUM-OXYGEN BATTERY (POSTPRINT...DOPED CARBON-GLASS CERAMIC CATHODE FOR HIGH PERFORMANCE LITHIUM-OXYGEN BATTERY (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c

  2. Conductive surface modification of LiFePO4 with nitrogen doped carbon layers for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Sukeun [ORNL; Liao, Chen [ORNL; Sun, Xiao-Guang [ORNL; Bridges, Craig A [ORNL; Unocic, Raymond R [ORNL; Nanda, Jagjit [ORNL; Dai, Sheng [ORNL; Paranthaman, Mariappan Parans [ORNL

    2012-01-01

    The LiFePO4 rod surface modified with nitrogen doped carbon layer has been prepared using hydrothermal processing followed by post-annealing in the presence of an ionic liquid. The coated LiFePO4 rod exhibits good capacity retention and high rate capability as the nitrogen doped carbon improves conductivity and prevents aggregation of the rod during cycling.

  3. Biophysical controls over concentration and depth distribution of soil organic carbon and nitrogen in desert playas

    Science.gov (United States)

    McKenna, Owen P.; Sala, Osvaldo E.

    2016-12-01

    Playa wetlands are important areas of soil organic carbon and nutrient storage in drylands. We conducted this study to assess how catchment biophysical variables control soil organic carbon and nitrogen in playas and how playas function differently than upland ecosystems. We found that playa organic carbon and nitrogen corresponded primarily with catchment vegetation cover and secondarily with catchment area, slope, and soil texture. The effect of increased organic matter production associated with high catchment vegetation cover overshadowed the potential effect of reduced run-on. We also found soil carbon and nitrogen profiles to be significantly shallower in playas than uplands. This trend is correlated with evidence of sedimentation and shallow-rooted plants in playas. Upland soils had a deeper carbon and nitrogen profile, which correlated with organic matter being generated by deeply rooted vegetation. In playas, C:N ratios remained constant through depth but in uplands, C:N ratios increased through depth. We found evidence that differences in rooting depth distributions and soil texture may explain these C:N variations between uplands and playas. In uplands, clay concentration increased with depth, whereas in playas, clay concentration did not change with depth, which highlighted the important role of sedimentation in these ecosystems. Our results suggest that small changes in playa catchment vegetation cover in response to climate change or grazing intensity would greatly impact playa soil organic carbon and nitrogen stocks. This effect would be due to the playa soils dependence on allochthonous organic matter and the large upland area that drains into playas.

  4. Oxygen and nitrogen-doped metal-free carbon catalysts for hydrochlorination of acetylene☆

    Institute of Scientific and Technical Information of China (English)

    Tongtong Zhang; Jia Zhao; Jiangtao Xu; Jinhui Xu; Xiaoxia Di; Xiaonian Li

    2016-01-01

    Activated carbon was tested as metal-free catalyst for hydrochlorination of acetylene in order to circumvent the problem of environment pollution caused by mercury and high cost by noble metals. Oxygen-doped and nitrogen-doped activated carbons were prepared and characterized by XPS, TPD and N2 physisorption methods. The influences of the surface functional groups on the catalytic performance were discussed base on these results. Among al the samples tested, a nitrogen-doped sample, AC-n-U500, exhibited the best performance, the acety-lene conversion being 92%and vinyl chloride selectivity above 99%at 240 °C and C2H2 hourly space velocity 30 h−1. Moreover, the AC-n-U500 catalyst exhibited a stable performance during a 200 h test with a conversion of acetylene higher than 76%at 210 °C at a C2H2 hourly space velocity 50 h−1. In contrary, oxygen-doped catalyst had lower catalytic activities. A linear relationship between the amount of pyrrolic-N and quaternary-N species and the catalytic activity was observed, indicating that these nitrogen-doped species might be the active sites and the key in tuning the catalytic performance. It is also found that the introduction of nitrogen species into the sample could significantly increase the adsorption amount of acetylene. The deactivation of nitrogen-doped activated carbon might be caused by the decrease of the accessibility to or the total amount of active sites.

  5. Pyrolysis of cellulose under ammonia leads to nitrogen-doped nanoporous carbon generated through methane formation.

    Science.gov (United States)

    Luo, Wei; Wang, Bao; Heron, Christopher G; Allen, Marshall J; Morre, Jeff; Maier, Claudia S; Stickle, William F; Ji, Xiulei

    2014-01-01

    Here, we present a simple one-step fabrication methodology for nitrogen-doped (N-doped) nanoporous carbon membranes via annealing cellulose filter paper under NH3. We found that nitrogen doping (up to 10.3 at %) occurs during cellulose pyrolysis under NH3 at as low as 550 °C. At 700 °C or above, N-doped carbon further reacts with NH3, resulting in a large surface area (up to 1973.3 m(2)/g). We discovered that the doped nitrogen, in fact, plays an important role in the reaction, leading to carbon gasification. CH4 was experimentally detected by mass spectrometry as a product in the reaction between N-doped carbon and NH3. When compared to conventional activated carbon (1533.6 m(2)/g), the N-doped nanoporous carbon (1326.5 m(2)/g) exhibits more than double the unit area capacitance (90 vs 41 mF/m(2)).

  6. A co-confined carbonization approach to aligned nitrogen-doped mesoporous carbon nanofibers and its application as an adsorbent

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Aibing, E-mail: chen_ab@163.com [College of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018 (China); Liu, Chao [College of Gemmology and Material Technics, Shijiazhuang University of Economic, Huaian Road 136, Shijiazhuang 050031 (China); Yu, Yifeng; Hu, Yongqi; Lv, Haijun; Zhang, Yue; Shen, Shufeng [College of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018 (China); Zhang, Jian, E-mail: jzhang@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2014-07-15

    Highlights: • MCNFs were synthesized by a co-confined carbonization method. • The diameter size of MCNFs with bimodal mesoporous structure can be modulated. • The obtained MCNFs manifest better adsorption capacity for SO{sub 2}, CO{sub 2} and Cd{sup 2+}. - Abstract: Nitrogen-doped carbon nanofibers (MCNFs) with an aligned mesoporous structure were synthesized by a co-confined carbonization method using anodic aluminum oxide (AAO) membrane and tetraethylorthosilicate (TEOS) as co-confined templates and ionic liquids as the precursor. The as-synthesized MCNFs with the diameter of 80–120 nm possessed a bulk nitrogen content of 5.3 wt% and bimodal mesoporous structure. The nitrogen atoms were mostly bound to the graphitic network in two forms, i.e. pyridinic and pyrrolic nitrogen, providing adsorption sites for acidic gases like SO{sub 2} and CO{sub 2}. Cyclic experiments revealed a considerable stability of MCNFs over 20 runs of SO{sub 2} adsorption and 15 runs for CO{sub 2} adsorption. The MCNFs also have a preferable adsorption performance for Cd{sup 2+}.

  7. Effects of Nitrogen and Carbon Sources on Transcription of Soluble Methyltransferases in Methanosarcina mazei Strain Gö1†

    OpenAIRE

    Veit, Katharina; Ehlers, Claudia; Schmitz, Ruth A.

    2005-01-01

    The methanogenic archaeon Methanosarcina mazei strain Gö1 uses versatile carbon sources and is able to fix molecular nitrogen with methanol as carbon and energy sources. Here, we demonstrate that when growing on trimethylamine (TMA), nitrogen fixation does not occur, indicating that ammonium released during TMA degradation is sufficient to serve as a nitrogen source and represses nif gene induction. We further report on the transcriptional regulation of soluble methyltransferases, which catal...

  8. Microtribology of Nitrogen-doped Amorphous Carbon Coatings

    Institute of Scientific and Technical Information of China (English)

    Dong F. Wang

    2004-01-01

    The friction, wear and lubrication of carbon nitride coatings on silicon substrates are studied using a spherical diamond counter-face with nano-scale asperities. The first part of this paper clarifies the coating thickness effect on frictional behavior of carbon nitride coatings. The second part of this paper reports empirical data on wear properties in repeated sliding contacts through in situ examination and post-sliding observation. The third part will concentrate on wear mechanisms for the transition from "No observable wear particles" to "Wear particle generation." In light of the above tribological study, the application of carbon nitride coatings to MicroElectroMechanical system (MEMS) is therefore discussed from view points of both microtribology and micromachining.

  9. Theoretical Investigation on Single-Wall Carbon Nanotubes Doped with Nitrogen, Pyridine-Like Nitrogen Defects, and Transition Metal Atoms

    Directory of Open Access Journals (Sweden)

    Michael Mananghaya

    2012-01-01

    Full Text Available This study addresses the inherent difficulty in synthesizing single-walled carbon nanotubes (SWCNTs with uniform chirality and well-defined electronic properties through the introduction of dopants, topological defects, and intercalation of metals. Depending on the desired application, one can modify the electronic and magnetic properties of SWCNTs through an appropriate introduction of imperfections. This scheme broadens the application areas of SWCNTs. Under this motivation, we present our ongoing investigations of the following models: (i (10, 0 and (5, 5 SWCNT doped with nitrogen (CNxNT, (ii (10, 0 and (5, 5 SWCNT with pyridine-like defects (3NV-CNxNT, (iii (10, 0 SWCNT with porphyrine-like defects (4ND-CNxNT. Models (ii and (iii were chemically functionalized with 14 transition metals (TMs: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag, Pt and Au. Using the spin-unrestricted density functional theory (DFT, stable configurations, deformations, formation and binding energies, the effects of the doping concentration of nitrogen, pyridine-like and porphyrine-like defects on the electronic properties were all examined. Results reveal that the electronic properties of SWCNTs show strong dependence on the concentration and configuration of nitrogen impurities, its defects, and the TMs adsorbed.

  10. Electrocatalytically switchable CO2 capture: first principle computational exploration of carbon nanotubes with pyridinic nitrogen.

    Science.gov (United States)

    Jiao, Yan; Zheng, Yao; Smith, Sean C; Du, Aijun; Zhu, Zhonghua

    2014-02-01

    Carbon nanotubes with specific nitrogen doping are proposed for controllable, highly selective, and reversible CO2 capture. Using density functional theory incorporating long-range dispersion corrections, we investigated the adsorption behavior of CO2 on (7,7) single-walled carbon nanotubes (CNTs) with several nitrogen doping configurations and varying charge states. Pyridinic-nitrogen incorporation in CNTs is found to induce an increasing CO2 adsorption strength with electron injecting, leading to a highly selective CO2 adsorption in comparison with N2 . This functionality could induce intrinsically reversible CO2 adsorption as capture/release can be controlled by switching the charge carrying state of the system on/off. This phenomenon is verified for a number of different models and theoretical methods, with clear ramifications for the possibility of implementation with a broader class of graphene-based materials. A scheme for the implementation of this remarkable reversible electrocatalytic CO2 -capture phenomenon is considered.

  11. Characteristics of nitrogen-doped carbon nanotubes synthesized by using PECVD and thermal CVD

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae-Bum; Kong, So-Jeo; Lee, Sung-Youp; Kim, Je-Han; Lee, Hyeong-Rag [Kyungpook National University, Daegu (Korea, Republic of); Kim, Chang-Duk [Kyungpook National University, Sangju (Korea, Republic of); Min, Bong-Ki [Yeungnam University, Gyeongsan (Korea, Republic of)

    2012-04-15

    Nitrogen-doped carbon nanotubes (N-CNTs) are synthesizd by using plasma-enhanced chemical vapor deposition (PECVD) and thermal chemical vapor deposition (TCVD) because PECVD and TCVD are attractive methods for producing N-CNTs. In this paper, we report the experimental observation of nitrogen incorporation in multiwalled carbon nanotubes grown by using these methods. XPS analysis indicates a shift and broadening of the C 1s spectra peak with increasing disorder induced by nitrogen doping. The N 1s XPS spectra of N-CNTs grown by using PECVD show various structures such as graphitic, pyridinic and N-gaseous forms, while N-CNTs grown by using TCVD have only a graphitic form. Each structure affects the electronic properties of N-CNTs in a different way. TCVD provides a more profitable synthesis method for n-type CNTs while PECVD supports the synthesis of activated N-CNTs with no post-treatment.

  12. Nitrogen fertilization effects on pasture photosynthesis, respiration, and ecosystem carbon content

    Science.gov (United States)

    Some studies have shown that increasing nitrogen (N) fertility can increase soil carbon (C) sequestration, whereas others suggest that N fertilization has no effect on sequestration. Increasing N fertilization typically increases annual photosynthetic C uptake (gross primary productivity or GPP) and...

  13. Novel porous carbon materials with ultrahigh nitrogen contents for selective CO 2 capture

    KAUST Repository

    Zhao, Yunfeng

    2012-01-01

    Nitrogen-doped carbon materials were prepared by a nanocasting route using tri-continuous mesoporous silica IBN-9 as a hard template. Rationally choosing carbon precursors and carefully controlling activation conditions result in an optimized material denoted as IBN9-NC1-A, which possesses a very high nitrogen doping concentration (∼13 wt%) and a large surface area of 890 m 2 g -1 arising from micropores (<1 nm). It exhibits an excellent performance for CO 2 adsorption over a wide range of CO 2 pressures. Specifically, its equilibrium CO 2 adsorption capacity at 25 °C reaches up to 4.50 mmol g -1 at 1 bar and 10.53 mmol g -1 at 8 bar. In particular, it shows a much higher CO 2 uptake at low pressure (e.g. 1.75 mmol g -1 at 25 °C and 0.2 bar) than any reported carbon-based materials, owing to its unprecedented nitrogen doping level. The high nitrogen contents also give rise to significantly enhanced CO 2/N 2 selectivities (up to 42), which combined with the high adsorption capacities, make these new carbon materials promising sorbents for selective CO 2 capture from power plant flue gas and other relevant applications. © 2012 The Royal Society of Chemistry.

  14. Cover crops for enriching soil carbon and nitrogen under bioenergy sorghum

    Science.gov (United States)

    Soil carbon (C) and nitrogen (N) can be enriched with cover crops under agronomic crops, but little is known about their enrichment under bioenergy crops. Legume (hairy vetch [Vicia villosa Roth]), nonlegume (rye [Secaele cereale L.]), a mixture of legume and nonlegume (hairy vetch and rye) and a co...

  15. Synthesis and drug detection performance of nitrogen-doped carbon dots

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Jingjing [Functional and Environment Materials Research Institute, College of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Nano Structure and Low Dimensional Physics Laboratory, Peking University, Beijing 100871 (China); Gao, Hui, E-mail: hope@lzu.edu.cn [Functional and Environment Materials Research Institute, College of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China)

    2014-05-01

    Recently, nitrogen-doped carbon dots (NCDs) have attracted considerable interest since nitrogen (N) doping could effectively tailor the electronic properties and the chemical reactivity of carbon dots (CDs) for advanced potential applications. Herein, a one-step pyrolysis method was presented for synthesizing the NCDs with excellent water solubility, good stability and a high quantum yield of ca. 28%. The detection performance of NCDs for the antibacterial drugs was further explored, and it was proved to effectively enhance the fluorescence due to the strong interaction between the NCDs and antibacterial drugs. - Highlights: • A facile yet economic bottom-up pyrolysis method for synthesizing nitrogen (N)-doped carbon dots (NCDs) using glutamic acid as the precursor. • Glutamic acid was the only starting material and used as a source of carbon and nitrogen; the formation and functionalization of NCDs were accomplished simultaneously. • The NCDs possess bright blue emission (with a high quantum yield of ca. 28%) and excellent excitation dependent on PL properties. • NCDs were used for the determination of antibacterial drugs based on the fluorescence enhancement.

  16. Disk Inoculum-Solid Medium Method To Test Carbon and Nitrogen Assimilation by Yeast Isolates

    OpenAIRE

    Moore, Kerry J.; Johnson, Michael G.; McClary, Shane P.

    1988-01-01

    Carbon and nitrogen assimilation for 50 yeasts isolated from White Riesling fermentation were tested by using a disk inoculum-solid medium method. This method was quicker and gave results comparable to the conventional liquid medium methods. Yeast characteristics (growth response, pigment production, morphology) could also be compared with this method.

  17. ANALYTICAL EMPLOYMENT OF STABLE ISOTOPES OF CARBON, NITROGEN, OXYGEN AND HYDROGEN FOR FOOD AUTHENTICATION

    Directory of Open Access Journals (Sweden)

    E. Novelli

    2011-04-01

    Full Text Available Stable isotopes of carbon, nitrogen, oxygen and hydrogen were used for analytical purposes for the discrimination of the type of production (farming vs. fishing in the case of sea bass and for geographical origin in the case of milk. These results corroborate similar experimental evidences and confirm the potential of this analytical tool to support of food traceability.

  18. Phase Equilibria of Three Binary Mixtures: Methanethiol + Methane, Methanethiol + Nitrogen, and Methanethiol + Carbon Dioxide

    DEFF Research Database (Denmark)

    Awan, Javeed; Tsivintzelis, Ioannis; Coquelet, Christophe;

    2012-01-01

    New vapor–liquid equilibrium (VLE) data for methanethiol (MM) + methane (CH4), methanethiol (MM) + nitrogen (N2), and methanethiol (MM) + carbon dioxide (CO2) is reported for temperatures of (304, 334, and 364) K in the pressure range (1 to 8) MPa. A “static–analytic” method was used for performi...

  19. Developing Ecological Models on Carbon and Nitrogen in Secondary Facultative Ponds

    Directory of Open Access Journals (Sweden)

    Aponte-Reyes Alexander

    2014-07-01

    Full Text Available Ecological models formulated for TOC, CO2, NH4+, NO3- and NTK, based in literature reviewed and field work were obtained monitoring three facultative secondary stabilization ponds, FSSP, pilots: conventional pond, CP, baffled pond, BP, and baffled-meshed pond, BMP. Models were sensitive to flow inlet, solar radiation, pH and oxygen content; the sensitive parameters in Carbon Model were KCOT Ba, umax Ba, umax Al, K1OX, VAl, R1DCH4, YBh. The sensitive parameters in the Nitrogen model were KCOT Ba, umax Ba, umax Al, VAl, KOPH, KOPA, r4An. The test t–paired showed a good simulating of Carbon model refers to TOC in FSSP; on the other side, the Nitrogen model showed a good simulating of NH4+. Different topological models modify ecosystem ecology forcing different transformation pathways of Nitrogen; equal transformations of the Carbon BMP topology could be achieved using lower volumes, however, a calibration for a new model would be required. Carbon and Nitrogen models developed could be coupled to hydrodynamics models for better modeling of FSSP.

  20. Fate of microbial nitrogen, carbon, hydrolysable amino acids, monosaccharides, and fatty acids in sediment

    NARCIS (Netherlands)

    Veuger, B.; van Oevelen, D.; Middelburg, J.J.

    2012-01-01

    The fate of microbial carbon, nitrogen, hydrolysable amino acids (HAAs), monosaccharides, and fatty acids in sediment was investigated experimentally. The microbial community of a tidal flat sediment was labeled with C-13-enriched glucose and N-15-enriched ammonium, and sediment was incubated for up

  1. Fate of microbial nitrogen, carbon, hydrolysable amino acids, monosaccharides, and fatty acids in sediment

    NARCIS (Netherlands)

    Veuger, B.; Van Oevelen, D.; Middelburg, J.J.

    2012-01-01

    The fate of microbial carbon, nitrogen, hydrolysable amino acids (HAAs), monosaccharides, and fatty acids in sediment was investigated experimentally. The microbial community of a tidal flat sediment was labeled with 13C-enriched glucose and 15N-enriched ammonium, and sediment was incubated for up t

  2. The ternary Fe-C-N system: Homogeneous distributions of nitrogen and carbon

    DEFF Research Database (Denmark)

    Brink, Bastian; Ståhl, Kenny; Christiansen, Thomas Lundin;

    2017-01-01

    of the nitriding and carburizing potentials, tailored nitrogen and carbon contents can be achieved, which allows assessment of a phase stability diagram for the Fe-N-C system, for which available experimental data is limited. Thermal decomposition sequences were established for the various iron carbides and (carbo...

  3. Carbon, Nitrogen, and Oxygen Abundances of Selected Stars in the Hertzsprung Gap

    Science.gov (United States)

    Vanture, Andrew D.; Wallerstein, George

    1999-01-01

    The iron, carbon, nitrogen, and oxygen abundances for several stars whose characteristics place them in the Hertzsprung gap have been derived from high-resolution spectra. These stars were selected based on the fact that previous studies have shown them to have peculiar carbon, nitrogen, or lithium abundances considering their position in the Hertzsprung-Russell diagram. When combined with the lithium abundances derived by Wallerstein and coworkers, the carbon, nitrogen, and oxygen abundances indicate that the sample of stars can generally be broken into two categories-lower luminosity dwarfs or subgiants that are unmixed and higher luminosity mixed giants. Among the sample are two stars, HR 7606 and HR 8626, which previously have been identified by Bidelman as ``low-velocity CH stars.'' These stars show metallicities of [Fe/H]~-0.5 and solar abundances of carbon, nitrogen, and oxygen. The strength of the CH band in these stars is probably an artifact of a mild metal deficiency and the absence of substantial mixing of CN processed materials to the surface of the star rather than an unusual nucleosynthetic history.

  4. Carbon respiration and nitrogen dynamics in Corsican pine litter amended with aluminium and tannins

    NARCIS (Netherlands)

    Kraal, P.; Nierop, K.G.J.; Kaal, J.; Tietema, A.

    2009-01-01

    We investigated the carbon (C) mineralisation and nitrogen (N) dynamics in litter from a Corsican pine forest in response to individual and combined additions of aluminium (M), condensed tannin (extracted from fresh Corsican pine needles) and hydrolysable tannin (commercial tannic acid). Production

  5. A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation

    NARCIS (Netherlands)

    Loisel, J.; Yu, Z.; Beilman, D.W.; Camill, P.; Alm, J.; Amesbury, M.J.; Anderson, D.; Andersson, S.; Bochicchio, C.; Barber, K.; Belyea, L.R.; Bunbury, J.; Chambers, F.M.; Charman, D.J.; De Vleeschouwer, F.; Fiałkiewicz-Kozieł, B.; Finkelstein, S.A.; Gałka, M.; Garneau, M.; Hammarlund, D; Hinchcliffe, W.; Holmquist, J.; Hughes, P.; Jones, M.C.; Klein, E.S.; Kokfelt, U.; Korhola, A.; Kuhry, P.; Lamarre, A.; Lamentowicz, M.; Large, D.; Lavoie, M.; Macdonald, G.; Magnan, G.; Mäkilä, M.; Mallon, G.; Mathijssen, P.; Mauquoy, D.; McCarroll, J.; Moore, T.R.; Nichols, J.; O'Reilly, B.; Oksanen, P.; Packalen, M.; Peteet, D.; Richard, P.J.H.; Robinson, S.; Ronkainen, T.; Rundgren, M.; Sannel, A.B.K.; Tarnocai, C.; Thom, T.; Tuittila, E.S.; Turetsky, M.; Väliranta, M.; van der Linden, M.; van Geel, B.; van Bellen, S.; Vitt, D.; Zhao, Y.; Zhou, W.

    2014-01-01

    Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45°N. It encompasses regions within which peat carb

  6. Carbon and nitrogen stocks in the soils of Central and Eastern Europe

    NARCIS (Netherlands)

    Batjes, N.H.

    2002-01-01

    Soil organic carbon and total nitrogen stocks are presented for Central and Eastern Europe. The study uses the soil geographic and attribute data held in a 1:2 500 000 scale Soil and Terrain (SOTER) database, covering Belarus, Bulgaria, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Moldova, P

  7. Contribution of chloroplast biogenesis to carbon-nitrogen balance during early leaf development in rice.

    Science.gov (United States)

    Kusumi, Kensuke; Hirotsuka, Shoko; Shimada, Hiroshi; Chono, Yoko; Matsuda, Osamu; Iba, Koh

    2010-07-01

    Chloroplast biogenesis is most significant during the changes in cellular organization associated with leaf development in higher plants. To examine the physiological relationship between developing chloroplasts and host leaf cells during early leaf development, we investigated changes in the carbon and nitrogen contents in leaves at the P4 developmental stage of rice, during which leaf blade structure is established and early events of chloroplast differentiation occur. During the P4 stage, carbon content on a dry mass basis remained constant, whereas the nitrogen content decreased by 30%. Among carbohydrates, sucrose and starch accumulated to high levels early in the P4 stage, and glucose, fructose and cellulose degradation increased during the mid-to-late P4 stage. In the chloroplast-deficient leaves of the virescent-1 mutant of rice, however, the carbon and nitrogen contents, as well as the C/N ratio during the P4 stage, were largely unaffected. These observations suggest that developing rice leaves function as sink organs at the P4 stage, and that chloroplast biogenesis and carbon and nitrogen metabolism in the leaf cell is regulated independently at this stage.

  8. Polyol synthesis in Aspergillus niger : influence of oxygen availability, carbon and nitrogen sources on the metabolism

    DEFF Research Database (Denmark)

    Diano, Audrey; Bekker-Jensen, S; Dynesen, Jens Østergaard

    2006-01-01

    Polyol production has been studied in Aspergillus niger under different conditions. Fermentations have been run using high concentration of glucose or xylose as carbon source and ammonium or nitrate as nitrogen source. The growth of biomass, as freely dispersed hyphae, led to an increase of medium...

  9. CARBON TO NITROGEN RATIO AND NITROGENOUS WASTE ACCUMULATION IN THE INTENSIVE CATFISH (Clarias gariepinus) CULTURE

    OpenAIRE

    Bambang Gunadi; Enang Harris; Eddy Supriyono; Sukenda Sukenda; Tatag Budiardi

    2011-01-01

    This experiment was carried out to determine the optimum C/N ratio for heterotrophic bacteria (biofloc) growth in order to control nitrogenous waste accumulation in the catfish (Clarias gariepinus) culture. Twenty fish with an initial individual size of about 50 g were stocked in fiberglass tanks which were filled with 200 L of water. Fish were fed with commercial floating fish feed with a protein level of 31%-33% (manufacturer label). The daily feeding rate was 2.5% of the fish biomass. The ...

  10. The effects of rising atmospheric carbon dioxide on shoot-root nitrogen and water signaling

    Directory of Open Access Journals (Sweden)

    Hsien Ming eEaslon

    2013-08-01

    Full Text Available Terrestrial higher plants are composed of roots and shoots, distinct organs that conduct complementary functions in dissimilar environments. For example, roots are responsible for acquiring water and nutrients such as inorganic nitrogen from the soil, yet shoots consume the majority of these resources. The success of such a relationship depends on excellent root-shoot communications. Increased net photosynthesis and decreased shoot nitrogen and water use at elevated CO2 fundamentally alter these source-sink relations. Lower than predicted productivity gains at elevated CO2 under nitrogen or water stress may indicate shoot-root signaling lacks plasticity to respond to rising atmospheric CO2 concentrations. The following presents recent research results on shoot-root nitrogen and water signaling, emphasizing the influence that rising atmospheric carbon dioxide levels are having on these source-sink interactions.

  11. Carbon and nitrogen mineralization in vineyard acid soils amended with a bentonitic winery waste

    Science.gov (United States)

    Fernández-Calviño, David; Rodríguez-Salgado, Isabel; Pérez-Rodríguez, Paula; Díaz-Raviña, Montserrat; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

    2015-04-01

    Carbon mineralization and nitrogen ammonification processes were determined in different vineyard soils. The measurements were performed in samples non-amended and amended with different bentonitic winery waste concentrations. Carbon mineralization was measured as CO2 released by the soil under laboratory conditions, whereas NH4+ was determined after its extraction with KCl 2M. The time evolution of both, carbon mineralization and nitrogen ammonification, was followed during 42 days. The released CO2 was low in the analyzed vineyard soils, and hence the metabolic activity in these soils was low. The addition of the bentonitic winery waste to the studied soils increased highly the carbon mineralization (2-5 fold), showing that the organic matter added together the bentonitic waste to the soil have low stability. In both cases, amended and non-amended samples, the maximum carbon mineralization was measured during the first days (2-4 days), decreasing as the incubation time increased. The NH4+ results showed an important effect of bentonitic winery waste on the ammonification behavior in the studied soils. In the non-amended samples the ammonification was no detected in none of the soils, whereas in the amended soils important NH4+ concentrations were detected. In these cases, the ammonification was fast, reaching the maximum values of NH4 between 7 and 14 days after the bentonitic waste additions. Also, the percentages of ammonification respect to the total nitrogen in the soil were high, showing that the nitrogen provided by the bentonitic waste to the soil is non-stable. The fast carbon mineralization found in the soils amended with bentonitic winery wastes shows low possibilities of the use of this waste for the increasing the organic carbon pools in the soil.On the other hand, the use of this waste as N-fertilizer can be possible. However, due its fast ammonification, the waste should be added to the soils during active plant growth periods.

  12. Atmospheric nitrogen deposition promotes carbon loss from peat bogs

    NARCIS (Netherlands)

    Bragazza, L.; Freeman, C.; Jones, T.; Rydin, H.; Limpens, J.; Fenner, N.; Ellis, T.; Gerdol, R.; Hajek, M.; Hajek, T.; Iacumin, P.; Kutnar, L.; Tahvanainen, T.; Toberman, H.

    2006-01-01

    Peat bogs have historically represented exceptional carbon (C) sinks because of their extremely low decomposition rates and consequent accumulation of plant remnants as peat. Among the factors favoring that peat accumulation, a major role is played by the chemical quality of plant litter itself, whi

  13. CARBON TO NITROGEN RATIO AND NITROGENOUS WASTE ACCUMULATION IN THE INTENSIVE CATFISH (Clarias gariepinus CULTURE

    Directory of Open Access Journals (Sweden)

    Bambang Gunadi

    2011-06-01

    Full Text Available This experiment was carried out to determine the optimum C/N ratio for heterotrophic bacteria (biofloc growth in order to control nitrogenous waste accumulation in the catfish (Clarias gariepinus culture. Twenty fish with an initial individual size of about 50 g were stocked in fiberglass tanks which were filled with 200 L of water. Fish were fed with commercial floating fish feed with a protein level of 31%-33% (manufacturer label. The daily feeding rate was 2.5% of the fish biomass. The inoculation of commercial Bacillus sp. isolates was applied in the first day of the experiment after fish stocking in order to obtain a bacterial density in water of 106 cfu/L. Molases was suplemented daily to the tanks to adjust C/N ratio in water. Four C/N ratios, i.e. 0, 7, 14, and 21, were applied as treatments in this experiment. The results showed that molasses suplementation up to C/N ratio 14 to 21 were able to support the growth of heterotrophic bacteria and to inhibit the accumulation of total ammonia nitrogen (TAN and nitrite in water therefore increase water quality for better growth of cultured catfish.

  14. Is plasticity in partitioning of photosynthetic resources between and within leaves important for whole-plant carbon gain in canopies?

    NARCIS (Netherlands)

    Pons, T.L.; Anten, N.P.R.

    2004-01-01

    1. The significance for whole-plant carbon gain of plasticity in between-leaf and within-leaf partitioning of photosynthetic resources was investigated using an experimental and modelling approach. Lysimachia vulgaris L. was grown at two contrasting stand densities and two levels of nutrient availab

  15. Evaluation of Natural Materials as Exogenous Carbon Sources for Biological Treatment of Low Carbon-to-Nitrogen Wastewater

    Science.gov (United States)

    Ramírez-Godínez, Juan; Beltrán-Hernández, Icela; Álvarez-Hernández, Alejandro; Coronel-Olivares, Claudia; Contreras-López, Elizabeth; Quezada-Cruz, Maribel; Vázquez-Rodríguez, Gabriela

    2015-01-01

    In the bacterial processes involved in the mitigation of nitrogen pollution, an adequately high carbon-to-nitrogen (C : N) ratio is key to sustain denitrification. We evaluated three natural materials (woodchips, barley grains, and peanut shells) as carbon sources for low C : N wastewater. The amount of organic matter released from these materials to aqueous media was evaluated, as well as their pollution swapping potential by measuring the release of total Kjeldahl nitrogen, N-NH4+, NO2−, and NO3−, and total phosphorous. Barley grains yielded the highest amount of organic matter, which also showed to be the most easily biodegradable. Woodchips and peanut shells released carbon rather steadily and so they would not require frequent replenishment from biological reactors. These materials produced eluates with lower concentrations of nutrients than the leachates from barley grains. However, as woodchips yielded lower amounts of suspended solids, they constitute an adequate exogenous source for the biological treatment of carbon-deficient effluents. PMID:26495313

  16. New catalyst supports prepared by surface modification of graphene- and carbon nanotube structures with nitrogen containing carbon coatings

    Science.gov (United States)

    Oh, Eun-Jin; Hempelmann, Rolf; Nica, Valentin; Radev, Ivan; Natter, Harald

    2017-02-01

    We present a new and facile method for preparation of nitrogen containing carbon coatings (NCC) on the surface of graphene- and carbon nanotubes (CNT), which has an increased electronic conductivity. The modified carbon system can be used as catalyst support for electrocatalytic applications, especially for polymer electrolyte membrane fuel cells (PEMFC). The surface modification is performed by impregnating carbon structures with a nitrogen containing ionic liquid (IL) with a defined C:N ratio, followed by a thermal treatment under ambient conditions. We investigate the influence of the main experimental parameters (IL amount, temperature, substrate morphology) on the formation of the NCC. Additionally, the structure and the chemical composition of the resulting products are analyzed by electron microscopic techniques (SEM, TEM), energy disperse X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and hot extraction analysis. The modified surface has a nitrogen content of 29 wt% which decreases strongly at temperatures above 600 °C. The new catalyst supports are used for the preparation of PEMFC anodes which are characterized by polarization measurements and electrochemical impedance spectroscopy (EIS). Compared to unmodified graphene and CNT samples the electronic conductivity of the modified systems is increased by a factor of 2 and shows improved mass transport properties.

  17. The experimental studies on the carbon and nitrogen budgets of Pseudeuphausia sinica

    Institute of Scientific and Technical Information of China (English)

    Guo Donghui; Li Shaojing; Chen Feng; Wang Guizhong; Chen Gang

    2003-01-01

    The carbon and nitrogen budgets were estimated on the adult females, juveniles and postfurcilia larvae of Pseudeuphausia sinica fed on newly hatching nauplii of Artemia salina in the laboratory. It was found that the ingestion rate was linearly related to the food concentration, suggesting high feeding potential. The linear correlation could be established between the respirating rate (carbon consumption rate) and carbon ingestion rate, as well as carbon assimilation rate. The regression coefficients (i.e.specific dynamic action coefficients) were in the range from 9% to 16% (ingested C) or 10% to 17% (assimilated C) respectively, with lower in the post-furcilia larvae. There also existed a linear correlation equation between estimated total nitrogen excretion rate and the rates of nitrogen ingestion and assimilation separately, except for the juveniles. The defecation rates increased with the increase of the ingestion rate; as a result, assimilation efficiency was not related to the ingestion rate, ranging from 0.84 to 0.95. The results inducated that the nitrogen content in food particles was a key factor limiting the growth of P. sinica. The critical ingestion rate was 10 μgN@mg-1body dry weight per day. Assimilated N was lost mostly by excretion, following allocated to somatic growth. The nitrogen loss by moult only accounted for a minor part. As for carbon budget, respiration and somatic growth also accounted for most of assimilation, but varied with ingestion rates. Moult loss was minor. Estimated reproductive growth (C&N) in the adult females accounted for somewhat higher percent of assimilation than the moult growth. The net growth efficiency (K2) increased with the increase of the ingestion rates, but decreased slightly for juvenile and post-furcilia larvae after the rates up to a certain value.

  18. Inversion of coupled carbon-nitrogen model parameters against multiple datasets using Markov chain Monte Carlo methodology

    Science.gov (United States)

    Yang, Y.; Zhou, X.; Weng, E.; Luo, Y.

    2010-12-01

    The Markov chain Monte Carlo (MCMC) method has been widely used to estimate terrestrial ecosystem model parameters. However, inverse analysis is now mainly applied to estimate parameters involved in terrestrial ecosystem carbon models, and yet not used to inverse terrestrial nitrogen model parameters. In this study, the Bayesian probability inversion and MCMC technique were applied to inverse model parameters in a coupled carbon-nitrogen model, and then the trained ecosystem model was used to predict nitrogen pool sizes at the Duke Forests FACE site. We used datasets of soil respiration, nitrogen mineralization, nitrogen uptake, carbon and nitrogen pools in wood, foliage, litterfall, microbial, forest floor, and mineral soil under ambient and elevated CO2 plots from 1996-2005. Our results showed that, the initial values of C pools in leaf, wood, root, litter, microbial and forest floor were well constrained. The transfer coefficients from pools of leaf biomass, woody biomass, root biomass, litter, forest floor were also well constrained by the actual measurements. The observed datasets gave moderate information to the transfer coefficient from the slow soil carbon pool. The parameters in nitrogen parts, such as C: N in plant, litter, and soil were also well constrained. In addition, parameters about nitrogen dynamics (i.e. nitrogen uptake, nitrogen loss, and nitrogen input through biological fixation and deposition) were also well constrained. The predicted carbon and nitrogen pool sizes using the constrained ecosystem models were well consistent with the observed values. Overall, these results suggest that the MCMC inversion technique is an effective method to synthesize information from various sources for predicting the responses of ecosystem carbon and nitrogen cycling to elevated CO2.

  19. Radiation and nitrogen use at the leaf and canopy level by wheat and oilseed rape during the critical period for grain number definition

    NARCIS (Netherlands)

    Dreccer, M.F.; Schapendonk, A.H.C.M.; Oijen, van M.; Pot, C.S.; Rabbinge, R.

    2000-01-01

    During the critical period for grain number definition, the amount of biomass produced per unit absorbed radiation is more sensitive to nitrogen (N) supply in oilseed rape than in wheat, and reaches a higher value at high N. This response was investigated by combining experimental and modelling work

  20. Synthesis of boron/nitrogen substituted carbons for aqueous asymmetric capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Tomko, Timothy [Energy and Mineral Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Rajagopalan, Ramakrishnan, E-mail: rur12@psu.edu [Materials Research Institute, Pennsylvania State University, 270 MRL Bldg., University Park, PA 16802 (United States); Aksoy, Parvana [Energy Institute, Pennsylvania State University, University Park, PA 16802 (United States); Foley, Henry C. [Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2011-06-01

    Highlights: > Synthesis of highly substituted boron and nitrogen containing carbons (BCN) for ultracapacitor applications. > Evidence for strong electroadsorption of protons on BCN. > Increased specific capacitance per unit area and improved cell voltage in aqueous asymmetric capacitors. - Abstract: Boron/nitrogen substituted carbons were synthesized by co-pyrolysis of polyborazylene/coal tar pitch blends to yield a carbon with a boron and nitrogen content of 14 at% and 10 at%, respectively. The presence of heteroatoms in these carbons shifted the hydrogen evolution overpotential to -1.4 V vs Ag/AgCl in aqueous electrolytes, providing a large electrochemical potential window ({approx}2.4 V) as well as a specific capacitance of 0.6 F/m{sup 2}. An asymmetric capacitor was fabricated using the as-prepared low surface area carbon as the negative electrode along with a redox active manganese dioxide as the positive electrode. The energy density of the capacitor exceeded 10 Wh/kg at a power density of 1 kW/kg and had a cycle life greater than 1000 cycles.

  1. Characterization of nitrogen doped silicon-carbon multi-layer nanostructures obtained by TVA method

    Science.gov (United States)

    Ciupina, Victor; Vasile, Eugeniu; Porosnicu, Corneliu; Prodan, Gabriel C.; Lungu, Cristian P.; Vladoiu, Rodica; Jepu, Ionut; Mandes, Aurelia; Dinca, Virginia; Caraiane, Aureliana; Nicolescu, Virginia; Dinca, Paul; Zaharia, Agripina

    2016-09-01

    Ionized nitrogen doped Si-C multi-layer thin films used to increase the oxidation resistance of carbon have been obtained by Thermionic Vacuum Arc (TVA) method. The 100 nm thickness carbon thin films were deposed on silicon or glass substrates and then seven N doped Si-C successively layers on carbon were deposed. To characterize the microstructure, tribological and electrical properties of as prepared N-SiC multi-layer films, Transmission Electron Microscopy (TEM, STEM), Energy Dispersive X-Ray Spectroscopy (EDXS), electrical and tribological techniques were achieved. Samples containing multi-layer N doped Si-C coating on carbon were investigated up to 1000°C. Oxidation protection is based on the reaction between SiC and elemental oxygen, resulting SiO2 and CO2, and also on the reaction involving N, O and Si-C, resulting silicon oxynitride (SiNxOy) with a continuously vary composition, and because nitrogen can acts as a trapping barrier for oxygen. The tribological properties of structures were studied using a tribometer with ball-on-disk configuration from CSM device with sapphire ball. The measurements show that the friction coefficient on the N-SiC is smaller than friction coefficient on uncoated carbon layer. Electrical conductivity at different temperatures was measured in constant current mode. The results confirm the fact that conductivity is greater when nitrogen content is greater. To justify the temperature dependence of conductivity we assume a thermally activated electrical transport mechanism.

  2. Corking Nitrogen-Doped Carbon Nanotube Cups with Gold Nanoparticles for Biodegradable Drug Delivery Applications.

    Science.gov (United States)

    Burkert, Seth C; Star, Alexander

    2015-12-02

    Carbon nanomaterials have been proposed as effective drug delivery devices; however their perceived biopersistence and toxicological profile may hinder their applications in medical therapeutics. Nitrogen doping of carbon nanotubes results in a unique "stacked-cup" structure, with cups held together through van der Waals forces. Disrupting these weak interactions yields individual and short-stacked nanocups that can subsequently be corked with gold nanoparticles, resulting in sealed containers for delivery of cargo. Peroxidase-catalyzed reactions can effectively uncork these containers, followed by complete degradation of the graphitic capsule, resulting in effective release of therapeutic cargo while minimizing harmful side effects. The protocols reported herein describe the synthesis of stacked nitrogen-doped carbon nanotube cups followed by effective separation into individual cups and gold nanoparticle cork formation resulting in loaded and sealed containers.

  3. COMPLEX COMPOST AND CIRCULATION OF NITROGEN AND CARBON AT THE AGROLANDSCAPE SYSTEMS

    Directory of Open Access Journals (Sweden)

    Belyuchenko I. S.

    2014-03-01

    Full Text Available Complex compost includes all elements of the periodic table and is valuable due to the complexity of its system. Among the elements forming a chemical composition of the complex compost we can identify two most important, which are distinguishing a specific character of the interaction with each other and defining the basic processes to ensure vegetation of living system - nitrogen and carbon. Nitrogen determines the rate of energy and connects with living forms of organic matter; it is included as the part of protein and is a major element in determining the productivity of ecosystems. At the cycle of carbon its organic forms and carbon dioxide take a part, presenting the main factors of the processes of respiration and photosynthesis

  4. Formation of complex Al-N-C layer in aluminium by successive carbon and nitrogen implantation

    Energy Technology Data Exchange (ETDEWEB)

    Uglov, V.V.; Cherenda, N.N. E-mail: info@research.bsu.unibel.by; Khodasevich, V.V.; Sokol, V.A.; Abramov, I.I.; Danilyuk, A.L.; Wenzel, A.; Gerlach, J.; Rauschenbach, B

    1999-01-01

    The results of Auger electron spectroscopy and transmission electron microscopy of the surface layer of aluminium after successive implantation by carbon and nitrogen ions are presented in this work. The energy of implanted ions is 40 keV. The implantation dose varies in the range (3.3-6.5)x10{sup 17} ions/cm{sup 2}. The findings show that successive implantation leads to the formation of two main layers in aluminium. The first layer is AlNC{sub x} (0carbon atoms form bonds with nitrogen atoms. The second layer contains disoriented Al{sub 4}C{sub 3} precipitates and carbon atoms migrated from the first layer. The mechanism of migration is discussed.

  5. Formation of complex Al-N-C layer in aluminium by successive carbon and nitrogen implantation

    Science.gov (United States)

    Uglov, V. V.; Cherenda, N. N.; Khodasevich, V. V.; Sokol, V. A.; Abramov, I. I.; Danilyuk, A. L.; Wenzel, A.; Gerlach, J.; Rauschenbach, B.

    1999-01-01

    The results of Auger electron spectroscopy and transmission electron microscopy of the surface layer of aluminium after successive implantation by carbon and nitrogen ions are presented in this work. The energy of implanted ions is 40 keV. The implantation dose varies in the range (3.3-6.5) × 10 17 ions/cm 2. The findings show that successive implantation leads to the formation of two main layers in aluminium. The first layer is AlNC x (0 < x < 0.5) layer with violated hcp. AlN structure, where carbon atoms form bonds with nitrogen atoms. The second layer contains disoriented Al 4C 3 precipitates and carbon atoms migrated from the first layer. The mechanism of migration is discussed.

  6. Latitudinal distributions of organic nitrogen and organic carbon in marine aerosols over the western North Pacific

    Directory of Open Access Journals (Sweden)

    Y. Miyazaki

    2010-11-01

    Full Text Available Marine aerosol samples were collected over the western North Pacific along the latitudinal transect from 44° N to 10° N in late summer 2008 for measurements of organic nitrogen (ON and organic carbon (OC as well as isotopic ratios of total nitrogen (TN and total carbon (TC. Increased concentrations of methanesulfonic acid (MSA and diethylammonium (DEA+ at 40–44° N and subtropical regions (10–20° N together with averaged satellite chlorophyll a data and 5-day back trajectories suggest a significant influence of marine biological activities on aerosols in these regions. ON exhibited increased concentrations up to 260 ngN m−3 in these marine biologically influenced aerosols. Water-insoluble organic nitrogen (WION was found to be the most abundant nitrogen in the aerosols, accounting for 55 ± 16% of total aerosol nitrogen. In particular, the average WION/ON ratio was as high as 0.93 ± 0.07 at 40–44° N. These results suggest that marine biological sources significantly contributed to ON, a majority of which is composed of water-insoluble fractions in the study region. Analysis of the stable carbon isotopic ratios (δ13C indicated that, on average, marine-derived carbon accounted for ~88 ± 12% of total carbon in the aerosols. In addition, the δ13C increased from −22 to −20‰ when ON/OC ratios increased from 0.15 to 0.35 in marine biologically influenced aerosols. These results clearly show that organic nitrogen is enriched in organic aerosols originated from an oceanic region with high biological productivity, indicating a preferential transfer of nitrogen-containing organic compounds from the sea surface to the marine atmosphere. Both WION concentrations and WION/water-insoluble organic carbon (WIOC ratios showed positive correlations with local wind speeds, suggesting that sea-to-air emissions of ON via sea spray significantly contributes to marine organic aerosols over the

  7. Latitudinal distributions of organic nitrogen and organic carbon in marine aerosols over the western North Pacific

    Directory of Open Access Journals (Sweden)

    Y. Miyazaki

    2011-04-01

    Full Text Available Marine aerosol samples were collected over the western North Pacific along the latitudinal transect from 44° N to 10° N in late summer 2008 for measurements of organic nitrogen (ON and organic carbon (OC as well as isotopic ratios of total nitrogen (TN and total carbon (TC. Increased concentrations of methanesulfonic acid (MSA and diethylammonium (DEA+ at 40–44° N and subtropical regions (10–20° N together with averaged satellite chlorophyll-a data and 5-day back trajectories suggest a significant influence of marine biological activities on aerosols in these regions. ON exhibited increased concentrations up to 260 ngN m−3 in these marine biologically influenced aerosols. Water-insoluble organic nitrogen (WION was found to be the most abundant nitrogen in the aerosols, accounting for 55 ± 16% of total aerosol nitrogen. In particular, the average WION/ON ratio was as high as 0.93 ± 0.07 at 40–44° N. These results suggest that marine biological sources significantly contributed to ON, a majority of which is composed of water-insoluble fractions in the study region. Analysis of the stable carbon isotopic ratios (δ13C indicated that, on average, marine-derived carbon accounted for ~88 ± 12% of total carbon in the aerosols. In addition, the δ13C showed higher values (from −22 to −20‰ when ON/OC ratios increased from 0.15 to 0.35 in marine biologically influenced aerosols. These results clearly show that organic nitrogen is enriched in organic aerosols originated from an oceanic region with high biological productivity, indicating a preferential transfer of nitrogen-containing organic compounds from the sea surface to the marine atmosphere. Both WION concentrations and WION/water-insoluble organic carbon (WIOC ratios tended to increase with increasing local wind speeds, indicating that sea-to-air emissions of ON via sea spray contribute significantly to the marine organic

  8. Soil carbon and nitrogen erosion in forested catchments: implications for erosion-induced terrestrial carbon sequestration

    Science.gov (United States)

    Stacy, E. M.; Hart, S. C.; Hunsaker, C. T.; Johnson, D. W.; Berhe, A. A.

    2015-08-01

    Lateral movement of organic matter (OM) due to erosion is now considered an important flux term in terrestrial carbon (C) and nitrogen (N) budgets, yet most published studies on the role of erosion focus on agricultural or grassland ecosystems. To date, little information is available on the rate and nature of OM eroded from forest ecosystems. We present annual sediment composition and yield, for water years 2005-2011, from eight catchments in the southern part of the Sierra Nevada, California. Sediment was compared to soil at three different landform positions from the source slopes to determine if there is selective transport of organic matter or different mineral particle size classes. Sediment export varied from 0.4 to 177 kg ha-1, while export of C in sediment was between 0.025 and 4.2 kg C ha-1 and export of N in sediment was between 0.001 and 0.04 kg N ha-1. Sediment yield and composition showed high interannual variation. In our study catchments, erosion laterally mobilized OM-rich litter material and topsoil, some of which enters streams owing to the catchment topography where steep slopes border stream channels. Annual lateral sediment export was positively and strongly correlated with stream discharge, while C and N concentrations were both negatively correlated with stream discharge; hence, C : N ratios were not strongly correlated to sediment yield. Our results suggest that stream discharge, more than sediment source, is a primary factor controlling the magnitude of C and N export from upland forest catchments. The OM-rich nature of eroded sediment raises important questions about the fate of the eroded OM. If a large fraction of the soil organic matter (SOM) eroded from forest ecosystems is lost during transport or after deposition, the contribution of forest ecosystems to the erosion-induced C sink is likely to be small (compared to croplands and grasslands).

  9. Fast Conversion of Ionic Liquids and Poly(Ionic Liquids into Porous Nitrogen-Doped Carbons in Air

    Directory of Open Access Journals (Sweden)

    Yongjun Men

    2016-04-01

    Full Text Available Ionic liquids and poly(ionic liquids have been successfully converted into nitrogen-doped porous carbons with tunable surface area up to 1200 m2/g at high temperatures in air. Compared to conventional carbonization process conducted under inert gas to produce nitrogen-doped carbons, the new production method was completed in a rather shorter time without noble gas protection.

  10. Simultaneous removal of COD and nitrogen using a novel carbon-membrane aerated biofilm reactor

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A membrane aerated biofilm reactor is a promising technology for wastewater treatment. In this study, a carbon-membrane aerated biofilm reactor (CMABR) has been developed, to remove carbon organics and nitrogen simultaneously from one reactor. The results showed that CMABR has a high chemical oxygen demand (COD) and nitrogen removal efficiency, as it is operated with a hydraulic retention time (HRT) of 20 h, and it also showed a perfect performance, even if the HRT was shortened to 12 h. In this period, the removal efficiencies of COD, ammonia nitrogen (NH4+-N), and total nitrogen (TN) reached 86%, 94%, and 84%, respectively. However,the removal efficiencies of NH4+-N and TN declined rapidly as the HRT was shortened to 8 h. This is because of the excessive growth of biomass on the nonwoven fiber and very high organic loading rate. The fluorescence in situ hybridization (FISH) analysis indicated that the ammonia oxidizing bacteria (AOB) were mainly distributed in the inner layer of the biofilm. The coexistence of AOB and eubacteria in one biofilm can enhance the simultaneous removal of COD and nitrogen.

  11. PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands

    Directory of Open Access Journals (Sweden)

    Y. Wu

    2013-03-01

    Full Text Available Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C and nitrogen (N cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1 daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2 competition among three plants functional types (PFTs, production and litter production of plants; (3 decomposition of peat; and (4 production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem.

  12. PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands

    Science.gov (United States)

    Wu, Y.; Blodau, C.

    2013-08-01

    Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C) and nitrogen (N) cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG) for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1) daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2) competition among three plants functional types (PFTs), production and litter production of plants; (3) decomposition of peat; and (4) production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem.

  13. Carbon and Nitrogen Sources Influence Tricalcium Phosphate Solubilization and Extracellular Phosphatase Activity by Talaromyces flavus.

    Science.gov (United States)

    Stefanoni Rubio, P J; Godoy, M S; Della Mónica, I F; Pettinari, M J; Godeas, A M; Scervino, J M

    2016-01-01

    The aim of this work was to study phosphate (P) solubilization (and the processes involved in this event) by Talaromyces flavus (BAFC 3125) as a function of carbon and/or nitrogen sources. P solubilization was evaluated in NBRIP media supplemented with different carbon (glucose, sorbitol, sucrose, and fructose) and nitrogen (L-asparagine, urea, ammonium sulfate (AS), and ammonium nitrate (AN) combinations. The highest P solubilization was related to the highest organic acid production (especially gluconic acid) and pH drop for those treatments where glucose was present. Also P solubilization was higher when an inorganic nitrogen source was supplemented to the media when compared to an organic one. Although not being present an organic P source, phosphatase activity was observed. This shows that P mineralization and P solubilization can occur simultaneously, and that P mineralization is not induced by the enzyme substrate. The combination that showed highest P solubilization was for AN-glucose. The highest acid phosphatase activity was for AS-fructose, while for alkaline phosphatase were for AS-fructose and AN-fructose. Acid phosphatase activity was higher than alkaline. P solubilization and phosphatase activity (acid and alkaline) were influenced by the different carbon-nitrogen combinations. A better understanding of phosphate-solubilizing fungi could bring a better use of soil P.

  14. Rectifying Properties of a Nitrogen/Boron-Doped Capped-Carbon-Nanotube-Based Molecular Junction

    Institute of Scientific and Technical Information of China (English)

    ZHAO Peng; LIU De-Sheng; ZHANG Ying; WANG Pei-Ji; ZHANG Zhong

    2011-01-01

    @@ Based on the non-equilibrium Green's function method and first-principles density functional theory calculations, we investigate the electronic transport properties of a nitrogen/boron-doped capped-single-walled carbonnanotube-based molecular junction.Obvious rectifying behavior is observed and it is strongly dependent on the doping site.The best rectifying performance can be carried out when the nitrogen/boron atom dopes at a carbon site in the second layer.Moreover, the rectifying performance can be further improved by adjusting the distance between the Cso nanotube caps.%Based on the non-equilibrium Green's function method and first-principles density functional theory calculations, we investigate the electronic transport properties of a nitrogen/boron-doped capped-single-walled carbon-nanotube-based molecular junction. Obvious rectifying behavior is observed and it is strongly dependent on the doping site. The best rectifying performance can be carried out when the nitrogen/boron atom dopes at a carbon site in the second layer. Moreover, the rectifying performance can be further improved by adjusting the distance between the C60 nanotube caps.

  15. Functionalization of terminal carbon atoms of hydroxyl terminated polybutadiene by polyazido nitrogen rich molecules

    Indian Academy of Sciences (India)

    Rajavelu Murali Sankar; Tapta Kanchan Roy; Tushar Jana

    2011-07-01

    We report a novel synthetic approach for the attachment of the polyazido nitrogen rich molecule on to the hydroxyl terminated polybutadiene (HTPB) backbone. The terminal carbon atoms of the HTPB are functionalized by attaching cyanuric chloride (CYC) covalently on the HTPB backbone. Further reaction of this modified HTPB with sodium azide yields polyazido nitrogen rich HTPB. The unique physico-chemical properties and the microstructure of the HTPB do not get affected upon modification. IR, gel permeable chromatography (GPC) and absorption spectroscopy studies prove that the polyazido nitrogen rich molecules are covalently attached at the terminal carbon atoms of the HTPB. The π electron delocalization owing to long butadiene chain, strong electron withdrawing effect of the triazine molecules are the major driving forces for the covalent attachment of the triazine at the terminal carbon atoms of the HTPB. The disruption of the intermolecular hydrogen bonding between the terminal hydroxyl groups of the HTPB chains and the presence of hydrogen bonding between the N atoms of the triazine ring with OH group of the HTPB are observed. Theoretical study also reveals the existence of the hydrogen bonding between the OH and N. Theoretical calculation shows that the detonation performance of the polyazido nitrogen rich HTPB are very promising.

  16. The key role of metal dopants in nitrogen-doped carbon xerogel for oxygen reduction reaction

    Science.gov (United States)

    Liu, Sisi; Deng, Chengwei; Yao, Lan; Zhong, Hexiang; Zhang, Huamin

    2014-12-01

    Highly active non-precious metal catalysts based on nitrogen-doped carbon xerogel (NCX) for the oxygen reduction reaction (ORR) is prepared with resorcinol(R)-formaldehyde (F) resin as carbon precursor and NH3 as nitrogen source. NCX samples doped with various transition metal species are investigated to elucidate the effect of transition metals on the structure and ORR activity of the products. As-prepared NCX catalysts with different metals are characterized using nitrogen-adsorption analysis, X-ray diffractometry, X-ray photoelectron spectroscopy, and Raman spectroscopy. The structural properties and ORR activities of the catalysts are altered by addition of different metals, and NCX doped with iron exhibits the best ORR activity. Metal doping evidently promotes the formation of more micropores and mesopores. Raman and XPS studies reveal that iron, cobalt, and nickel can increase pyridinic-N contents and that iron can catalyse the formation of graphene structures and enhance quaternary-N contents. Whereas the total N-content does not determine ORR activity, Metal-N4/C-like species generated from the interaction of the metals with nitrogen and carbon atoms play important roles in achieving high ORR activity.

  17. Lithium and sodium storage in highly ordered mesoporous nitrogen-doped carbons derived from honey

    Science.gov (United States)

    Zhang, Yongzhi; Chen, Li; Meng, Yan; Xie, Jun; Guo, Yong; Xiao, Dan

    2016-12-01

    Honey, a widely existent biomass, consists mainly of carbohydrate and other nitrogen-containing substances such as proteins, enzymes and organic acids. It can be mixed homogeneously with mesoporous silica template for its excellent water-solubility and moderate viscosity. In this work, honey was employed as a nitrogen-containing carbon precursor to prepare nitrogen-doped ordered mesoporous carbons (OMCs). The obtained honey derived mesoporous nitrogen-doped carbons (HMNCs) with dilated interlayer spacings of 0.387-0.395 nm, narrow pore size distributions centering at around 4 nm and satisfactory N contents of 1.38-4.32 wt% offer superb dual functionality for lithium ion battery (LIB) and sodium ion battery (NIB) anodes. Tested against Li, the optimized HMNC-700 delivers a superior reversible capacity of 1359 mA h g-1 after 10 cycles at 100 mA g-1 and excellent rate capability and cycling stability of 722 mA h g-1 after 200 cycles at 1 A g-1. For NIB applications, HMNC-700 offers a high initial reversible capacity of 427 mA h g-1 and stable reversible capacity of 394 mA h g-1 at 100 mA g-1.

  18. Nitrogen Doped Macroporous Carbon as Electrode Materials for High Capacity of Supercapacitor

    Directory of Open Access Journals (Sweden)

    Yudong Li

    2017-01-01

    Full Text Available Nitrogen doped carbon materials as electrodes of supercapacitors have attracted abundant attention. Herein, we demonstrated a method to synthesize N-doped macroporous carbon materials (NMC with continuous channels and large size pores carbonized from polyaniline using multiporous silica beads as sacrificial templates to act as electrode materials in supercapacitors. By the nice carbonized process, i.e., pre-carbonization at 400 °C and then pyrolysis at 700/800/900/1000 °C, NMC replicas with high BET specific surface areas exhibit excellent stability and recyclability as well as superb capacitance behavior (~413 F ⋅ g−1 in alkaline electrolyte. This research may provide a method to synthesize macroporous materials with continuous channels and hierarchical pores to enhance the infiltration and mass transfer not only used as electrode, but also as catalyst somewhere micro- or mesopores do not work well.

  19. Nitrogen input effectiveness on carbon sequestration in rainfed cropping system

    Science.gov (United States)

    Novara, Agata; Gristina, Luciano; Poma, Ignazio

    2016-04-01

    The combined effect of total N and C/N ratio had a large influence on the decomposition rate and consequently on potential soil organic carbon sequestration. The aim of the work was to evaluate Carbon sequestration potentiality under three mineral N fertilization levels in interaction with two cropping systems characterized by addition of N input due to leguminous species in the rotation. The study was carried out in the semiarid Mediterranean environment in a 18years long-term experiment. Is well know that in the semiarid environment the excess of N fertilization reduces biomass yield and the consequent C input. On the contrary, both N and C input determine high difference in C/N input ratio and faster organic matter mineralization. Results showed no influence of N fertilization on SOC sequestration and a reduction of SOC stock due to crop rotation due to lower C input. Crop residue quality of durum wheat-pea crop rotation characterized by a faster decomposition rate could explain the lower ability of crop rotation to sequester C in the semiarid environment.

  20. Comparative genomic analysis of carbon and nitrogen assimilation mechanisms in three indigenous bioleaching bacteria: predictions and validations

    Directory of Open Access Journals (Sweden)

    Ehrenfeld Nicole

    2008-12-01

    Full Text Available Abstract Background Carbon and nitrogen fixation are essential pathways for autotrophic bacteria living in extreme environments. These bacteria can use carbon dioxide directly from the air as their sole carbon source and can use different sources of nitrogen such as ammonia, nitrate, nitrite, or even nitrogen from the air. To have a better understanding of how these processes occur and to determine how we can make them more efficient, a comparative genomic analysis of three bioleaching bacteria isolated from mine sites in Chile was performed. This study demonstrated that there are important differences in the carbon dioxide and nitrogen fixation mechanisms among bioleaching bacteria that coexist in mining environments. Results In this study, we probed that both Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans incorporate CO2 via the Calvin-Benson-Bassham cycle; however, the former bacterium has two copies of the Rubisco type I gene whereas the latter has only one copy. In contrast, we demonstrated that Leptospirillum ferriphilum utilizes the reductive tricarboxylic acid cycle for carbon fixation. Although all the species analyzed in our study can incorporate ammonia by an ammonia transporter, we demonstrated that Acidithiobacillus thiooxidans could also assimilate nitrate and nitrite but only Acidithiobacillus ferrooxidans could fix nitrogen directly from the air. Conclusion The current study utilized genomic and molecular evidence to verify carbon and nitrogen fixation mechanisms for three bioleaching bacteria and provided an analysis of the potential regulatory pathways and functional networks that control carbon and nitrogen fixation in these microorganisms.

  1. Canopy position affects the relationships between leaf respiration and associated traits in a tropical rainforest in Far North Queensland.

    Science.gov (United States)

    Weerasinghe, Lasantha K; Creek, Danielle; Crous, Kristine Y; Xiang, Shuang; Liddell, Michael J; Turnbull, Matthew H; Atkin, Owen K

    2014-06-01

    We explored the impact of canopy position on leaf respiration (R) and associated traits in tree and shrub species growing in a lowland tropical rainforest in Far North Queensland, Australia. The range of traits quantified included: leaf R in darkness (RD) and in the light (RL; estimated using the Kok method); the temperature (T)-sensitivity of RD; light-saturated photosynthesis (Asat); leaf dry mass per unit area (LMA); and concentrations of leaf nitrogen (N), phosphorus (P), soluble sugars and starch. We found that LMA, and area-based N, P, sugars and starch concentrations were all higher in sun-exposed/upper canopy leaves, compared with their shaded/lower canopy and deep-shade/understory counterparts; similarly, area-based rates of RD, RL and Asat (at 28 °C) were all higher in the upper canopy leaves, indicating higher metabolic capacity in the upper canopy. The extent to which light inhibited R did not differ significantly between upper and lower canopy leaves, with the overall average inhibition being 32% across both canopy levels. Log-log RD-Asat relationships differed between upper and lower canopy leaves, with upper canopy leaves exhibiting higher rates of RD for a given Asat (both on an area and mass basis), as well as higher mass-based rates of RD for a given [N] and [P]. Over the 25-45 °C range, the T-sensitivity of RD was similar in upper and lower canopy leaves, with both canopy positions exhibiting Q10 values near 2.0 (i.e., doubling for every 10 °C rise in T) and Tmax values near 60 °C (i.e., T where RD reached maximal values). Thus, while rates of RD at 28 °C decreased with increasing depth in the canopy, the T-dependence of RD remained constant; these findings have important implications for vegetation-climate models that seek to predict carbon fluxes between tropical lowland rainforests and the atmosphere.

  2. Increased forest carbon storage with increased atmospheric CO2 despite nitrogen limitation: a game-theoretic allocation model for trees in competition for nitrogen and light.

    Science.gov (United States)

    Dybzinski, Ray; Farrior, Caroline E; Pacala, Stephen W

    2015-03-01

    Changes in resource availability often cause competitively driven changes in tree allocation to foliage, wood, and fine roots, either via plastic changes within individuals or through turnover of individuals with differing strategies. Here, we investigate how optimally competitive tree allocation should change in response to elevated atmospheric CO2 along a gradient of nitrogen and light availability, together with how those changes should affect carbon storage in living biomass. We present a physiologically-based forest model that includes the primary functions of wood and nitrogen. From a tree's perspective, wood is an offensive and defensive weapon used against neighbors in competition for light. From a biogeochemical perspective, wood is the primary living reservoir of stored carbon. Nitrogen constitutes a tree's photosynthetic machinery and the support systems for that machinery, and its limited availability thus reduces a tree's ability to fix carbon. This model has been previously successful in predicting allocation to foliage, wood, and fine roots along natural productivity gradients. Using game theory, we solve the model for competitively optimal foliage, wood, and fine root allocation strategies for trees in competition for nitrogen and light as a function of CO2 and nitrogen mineralization rate. Instead of down-regulating under nitrogen limitation, carbon storage under elevated CO2 relative to carbon storage at ambient CO2 is approximately independent of the nitrogen mineralization rate. This surprising prediction is a consequence of both increased competition for nitrogen driving increased fine root biomass and increased competition for light driving increased allocation to wood under elevated CO2 .

  3. Adsorption behaviors of methyl orange dye on nitrogen-doped mesoporous carbon materials.

    Science.gov (United States)

    Li, He; An, Nihong; Liu, Gang; Li, Jialu; Liu, Na; Jia, Mingjun; Zhang, Wenxiang; Yuan, Xiaoling

    2016-03-15

    A series of nitrogen-doped mesoporous carbon materials (NMC) with different nitrogen contents (from 9.1 to 11.3 wt.%) were prepared using urea and ammonia as economical nitrogen resources by sol-gel method. The NMC materials possessed high surface areas (from 659 m(2)/g to 912 m(2)/g) as well as large number of oxygen-containing and nitrogen-containing groups. The adsorption behaviors of NMC materials for anionic dye methyl orange (MO) were investigated, which are fit excellent for the Langmuir isothermal adsorption equation. All the materials exhibited high adsorption capacity for MO at room temperature. Their adsorption capacity can be adjusted by changing the nitrogen contents in NMC materials. Moreover, treating the NMC material at higher temperature can significantly improve the adsorption capacity for MO. According to the results of characterization, the main features of NMC materials, like large pore size and abundant basic nitrogen-containing groups on the surface, should be related to the excellent adsorption property for MO.

  4. Nitrogen accumulation tracks carbon in multispecies system under elevated CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, H.B.; Polley, H.W.; Mayeux, H.S. [USDA-ARS, Temple, TX (United States)

    1995-09-01

    The woody legume Acacia smallii (huisache), and two perennial grasses, Schizachyrium scoparium (little bluestem) and Stipa leucotricha (Texas wintergrass) were grown as monocultures and in mixture under CO{sub 2} concentrations of 370, 700, and 1000 {mu}L/L for more than two years. The fine sandy loam soil was unfertilized, enriched in N15, and inoculated with huisache rhizobia. Elevated CO{sub 2} stimulated nitrogen fixation by huisache. After one year 33%, 64% and 76% of foliar N in the woody legume was ascribable to nitrogen fixation in the 370, 700 and 1000 {mu}L/L treatments, respectively. Percent nitrogen content of shoots decreased as CO{sub 2} increased (28% in 700 {mu}L/L and 34% 1000 {mu}L/L) relative to 370 {mu}L/L but the total nitrogen/plant increased 74% and 108% for these same concentrations due to greater plant biomass produced in the elevated CO{sub 2}. In the grass mixtures atmospheric nitrogen fixed by the wintergrass from mixtures was reduced relative to monocultures while the %N concentration was increased. These results suggest that a positive feedback between elevated CO{sub 2} and nitrogen accumulation may exist in multispecies systems containing legumes which can enhance the response of terrestrial carbon fixation to rising CO{sub 2}.

  5. Effects of nitrogen and carbon sources on the production of inulinase from strain Bacillus sp. SG113

    Science.gov (United States)

    Gavrailov, Simeon; Ivanova, Viara

    2016-03-01

    The effects of the carbon and nitrogen substrates on the growth of Bacillus sp. SG113 strain were studied. The use of organic nitrogen sources (peptone, beef extract, yeast extract, casein) leads to rapid cellular growth and the best results for the Bacillus strain were obtained with casein hydrolysate. From the inorganic nitrogen sources studied, the (NH4) 2SO4 proved to be the best nitrogen source. Casein hydrolysate and (NH4) 2SO4 stimulated the invertase synthesis. In the presence of Jerusalem artichoke, onion and garlic extracts as carbon sources the strain synthesized from 6 to 10 times more inulinase.

  6. Enhancement of oxygen reduction activity of nanoshell carbons by introducing nitrogen atoms from metal phthalocyanines

    Energy Technology Data Exchange (ETDEWEB)

    Ozaki, Jun-ichi, E-mail: jozaki@cee.gunma-u.ac.j [Department of Chemical and Environmental Engineering, Graduate School of Engineering, Gunma University, 1-5-1, Tenjin-cho, Kiryu, Gunma 376-8515 (Japan); Tanifuji, Shin-ichi; Furuichi, Atsuya; Yabutsuka, Katsutoshi [Department of Chemical and Environmental Engineering, Graduate School of Engineering, Gunma University, 1-5-1, Tenjin-cho, Kiryu, Gunma 376-8515 (Japan)

    2010-02-15

    Nanoshell carbon is a type of catalytically grown nanocarbon with a hollow, round, shell-like structure, with a diameter in the range of approximately 20-50 nm. It has been shown to possess the electrocatalytic activity for oxygen reduction reaction (ORR) and is also expected to be a non-Pt catalyst for polymer electrolyte fuel cells. This paper reports the synergetic enhancement of the ORR activity of nanoshell carbons caused by the coexistence of nitrogen atoms. The nanoshell carbons were prepared by the carbonization of furan resin in the presence of acetylacetonates (AAs) and of phthalocyanines (Pcs), which contained Fe, Co, and Ni. The Pc-derived nanoshells (MP-T series; M = Co or Fe, T = carbonization temperature) showed higher ORR activities than the AA-derived nanoshells (MA-T series; M = Co or Fe, T = carbonization temperature) when the same metal elements were employed. An XPS study revealed that nitrogen species were introduced to the surface of the nanoshells when Pcs were used as the nanoshell-forming catalysts, and that no metal species remained on the nanoshells. Principally, the ORR activity of the carbons was governed by the presence of the nanoshells and further enhancement could be achieved by the introduction of nitrogen atoms. 0.78 V of OCV and 0.21 W cm{sup -2} of the maximum power density were observed for a fuel cell whose MEA consisted of 3CoP1000 cathode and a commercial Pt/C anode, when it was operated at 80 deg. C under a pressurized condition of 0.35 MPa.

  7. Nitrogen reduction pathways in estuarine sediments: Influences of organic carbon and sulfide

    Science.gov (United States)

    Plummer, Patrick; Tobias, Craig; Cady, David

    2015-10-01

    Potential rates of sediment denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) were mapped across the entire Niantic River Estuary, CT, USA, at 100-200 m scale resolution consisting of 60 stations. On the estuary scale, denitrification accounted for ~ 90% of the nitrogen reduction, followed by DNRA and anammox. However, the relative importance of these reactions to each other was not evenly distributed through the estuary. A Nitrogen Retention Index (NIRI) was calculated from the rate data (DNRA/(denitrification + anammox)) as a metric to assess the relative amounts of reactive nitrogen being recycled versus retained in the sediments following reduction. The distribution of rates and accompanying sediment geochemical analytes suggested variable controls on specific reactions, and on the NIRI, depending on position in the estuary and that these controls were linked to organic carbon abundance, organic carbon source, and pore water sulfide concentration. The relationship between NIRI and organic carbon abundance was dependent on organic carbon source. Sulfide proved the single best predictor of NIRI, accounting for 44% of its observed variance throughout the whole estuary. We suggest that as a single metric, sulfide may have utility as a proxy for gauging the distribution of denitrification, anammox, and DNRA.

  8. Hierarchical porous nitrogen-doped partial graphitized carbon monoliths for supercapacitor

    Science.gov (United States)

    Yu, Yifeng; Du, Juan; Liu, Lei; Wang, Guoxu; Zhang, Hongliang; Chen, Aibing

    2017-03-01

    Porous carbon monoliths have attracted great interest in many fields due to their easy availability, large specific surface area, desirable electronic conductivity, and tunable pore structure. In this work, hierarchical porous nitrogen-doped partial graphitized carbon monoliths (N-MC-Fe) with ordered mesoporous have been successfully synthesized by using resorcinol-formaldehyde as precursors, iron salts as catalyst, and mixed triblock copolymers as templates via a one-step hydrothermal method. In the reactant system, hexamethylenetetramine (HMT) is used as nitrogen source and one of the carbon precursors under hydrothermal conditions instead of using toxic formaldehyde. The N-MC-Fe show hierarchically porous structures, with interconnected macroporous and ordered hexagonally arranged mesoporous. Nitrogen element is in situ doped into carbon through decomposition of HMT. Iron catalyst is helpful to improve the graphitization degree and pore volume of N-MC-Fe. The synthesis strategy is user-friendly, cost-effective, and can be easily scaled up for production. As supercapacitors, the N-MC-Fe show good capacity with high specific capacitance and good electrochemical stability.

  9. Spatial and Temporal Patterns of Soil Carbon and Nitrogen Storage Following Woody Plant Encroachment Into Grassland

    Science.gov (United States)

    Archer, S.; Boutton, T. W.; Wu, X. B.; Liu, F.; Bai, E.

    2004-12-01

    Encroachment of woody plants into drylands during the past century may have significantly influenced the terrestrial carbon cycle. However, the magnitude and sign of change in soil organic carbon (SOC) pools accompanying this vegetation change is highly uncertain, ranging from positive to neutral to negative. Some of the controversy over woody plant impacts on SOC pools may be an artifact how soil properties determined from point samples are area-weighted and extrapolated. If there is substantial spatial structure in properties of soils associated with woody and herbaceous communities, extrapolations from limited point samples that do not account for this may over- or underestimate actual SOC pools. To test this possibility, we quantified near surface (0-15 cm) soil properties (bulk density, SOC, total N [TN], root biomass) at seven locations along transects extending from the tree bole to canopy edge and into adjoining herbaceous zones in replicated woody communities known to have developed on grasslands over the past 100 y. A strong gradient was found to occur: root biomass, SOC, and TN decreased exponentially with distance from tree boles, while bulk density increased. These spatial changes are consistent with temporal changes expected to occur as shrub establish and their canopies grow through time. Given the strong spatial structure of the data, it appears that area-weighted extrapolations of SOC based on near-bole samples would overestimate woody plant influences, whereas sampling soils away from boles would tend to underestimate impacts. Implications for sampling strategies to efficiently and effectively represent this non-linear spatial variation will be discussed.

  10. Integration of Carbon, Nitrogen, and Oxygen Metabolism in Escherichia coli--Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Rabinowitz, Joshua D; Wingreen, Ned s; Rabitz, Herschel A; Xu, Yifan

    2012-10-22

    A key challenge for living systems is balancing utilization of multiple elemental nutrients, such as carbon, nitrogen, and oxygen, whose availability is subject to environmental fluctuations. As growth can be limited by the scarcity of any one nutrient, the rate at which each nutrient is assimilated must be sensitive not only to its own availability, but also to that of other nutrients. Remarkably, across diverse nutrient conditions, E. coli grows nearly optimally, balancing effectively the conversion of carbon into energy versus biomass. To investigate the link between the metabolism of different nutrients, we quantified metabolic responses to nutrient perturbations using LC-MS based metabolomics and built differential equation models that bridge multiple nutrient systems. We discovered that the carbonaceous substrate of nitrogen assimilation, -ketoglutarate, directly inhibits glucose uptake and that the upstream glycolytic metabolite, fructose-1,6-bisphosphate, ultrasensitively regulates anaplerosis to allow rapid adaptation to changing carbon availability. We also showed that NADH controls the metabolic response to changing oxygen levels. Our findings support a general mechanism for nutrient integration: limitation for a nutrient other than carbon leads to build-up of the most closely related product of carbon metabolism, which in turn feedback inhibits further carbon uptake.

  11. QQS orphan gene regulates carbon and nitrogen partitioning across species via NF-YC interactions.

    Science.gov (United States)

    Li, Ling; Zheng, Wenguang; Zhu, Yanbing; Ye, Huaxun; Tang, Buyun; Arendsee, Zebulun W; Jones, Dallas; Li, Ruoran; Ortiz, Diego; Zhao, Xuefeng; Du, Chuanlong; Nettleton, Dan; Scott, M Paul; Salas-Fernandez, Maria G; Yin, Yanhai; Wurtele, Eve Syrkin

    2015-11-24

    The allocation of carbon and nitrogen resources to the synthesis of plant proteins, carbohydrates, and lipids is complex and under the control of many genes; much remains to be understood about this process. QQS (Qua-Quine Starch; At3g30720), an orphan gene unique to Arabidopsis thaliana, regulates metabolic processes affecting carbon and nitrogen partitioning among proteins and carbohydrates, modulating leaf and seed composition in Arabidopsis and soybean. Here the universality of QQS function in modulating carbon and nitrogen allocation is exemplified by a series of transgenic experiments. We show that ectopic expression of QQS increases soybean protein independent of the genetic background and original protein content of the cultivar. Furthermore, transgenic QQS expression increases the protein content of maize, a C4 species (a species that uses 4-carbon photosynthesis), and rice, a protein-poor agronomic crop, both highly divergent from Arabidopsis. We determine that QQS protein binds to the transcriptional regulator AtNF-YC4 (Arabidopsis nuclear factor Y, subunit C4). Overexpression of AtNF-YC4 in Arabidopsis mimics the QQS-overexpression phenotype, increasing protein and decreasing starch levels. NF-YC, a component of the NF-Y complex, is conserved across eukaryotes. The NF-YC4 homologs of soybean, rice, and maize also bind to QQS, which provides an explanation of how QQS can act in species where it does not occur endogenously. These findings are, to our knowledge, the first insight into the mechanism of action of QQS in modulating carbon and nitrogen allocation across species. They have major implications for the emergence and function of orphan genes, and identify a nontransgenic strategy for modulating protein levels in crop species, a trait of great agronomic significance.

  12. Carbon and nitrogen isotope systematics in diamond: Different sensitivities to isotopic fractionation or a decoupled origin?

    Science.gov (United States)

    Hogberg, K.; Stachel, T.; Stern, R. A.

    2016-11-01

    Using stable isotope data obtained on multiple aliquots of diamonds from worldwide sources, it has been argued that carbon and nitrogen in diamond are decoupled. Here we re-investigate the carbon-nitrogen relationship based on the most comprehensive microbeam data set to date of stable isotopes and nitrogen concentrations in diamonds (n = 94) from a single locality. Our diamond samples, derived from two kimberlites in the Chidliak Field (NE Canada), show large variability in δ13C (- 28.4 ‰ to - 1.1‰, mode at - 5.8‰), δ15N (- 5.8 to + 18.8‰, mode at - 3.0‰) and nitrogen contents ([N]; 3800 to less than 1 at.ppm). In combination, cathodoluminescence imaging and microbeam analyses reveal that the diamonds grew from multiple fluid pulses, with at least one major hiatus documented in some samples that was associated with a resorption event and an abrupt change from low δ13C and [N] to mantle-like δ13C and high [N]. Overall, δ13C appears to be uncorrelated to δ15N and [N] on both the inter- and intra-diamond levels. Co-variations of δ15N-log[N], however, result in at least two parallel, negatively correlated linear arrays, which are also present on the level of the individual diamonds falling on these two trends. These arrays emerge from the two principal data clusters, are characterized by slightly negative and slightly positive δ15N (about - 3 and + 2‰, respectively) and variable but overall high [N]. Using published values for the diamond-fluid nitrogen isotope fractionation factor and nitrogen partition coefficient, these trends are perfectly reproduced by a Rayleigh fractionation model. Overall, three key elements are identified in the formation of the diamond suite studied: (1.) a low δ13C and low [N] component that possibly is directly associated with an eclogitic diamond substrate or introduced during an early stage fluid event. (2.) Repeated influx of a variably nitrogen-rich mantle fluid (mildly negative δ13C and δ15N). (3.) In waning

  13. Enhanced Fuel Cell Catalyst Durability with Nitrogen Modified Carbon Supports

    Science.gov (United States)

    2013-02-12

    1000 mg of commercially available carbon powder (Cabot Vulcan XCR72R) was placed into the barrel and the chamber was evacuated to approximately 1 × 10−6...unmodified and N-modified Vulcan were obtained on a Philips CM200 TEM. X-ray Photoelectron Spectroscopy (XPS) analysis of the synthesized catalysts was done...durability cycles Pt-Ru/ Vulcan 73 3.3 × 10−5 24 51 10 Pt-Ru/N- Vulcan 55 2.9 × 10−5 17 60 40 Pt-Ru/C JM 5000 69 3.0 × 10−5 20 48 17 tials higher than 0.7 V

  14. Improved Electrochemical Performance of LiFePO4@N-Doped Carbon Nanocomposites Using Polybenzoxazine as Nitrogen and Carbon Sources.

    Science.gov (United States)

    Wang, Ping; Zhang, Geng; Li, Zhichen; Sheng, Wangjian; Zhang, Yichi; Gu, Jiangjiang; Zheng, Xinsheng; Cao, Feifei

    2016-10-03

    Polybenzoxazine is used as a novel carbon and nitrogen source for coating LiFePO4 to obtain LiFePO4@nitrogen-doped carbon (LFP@NC) nanocomposites. The nitrogen-doped graphene-like carbon that is in situ coated on nanometer-sized LiFePO4 particles can effectively enhance the electrical conductivity and provide fast Li(+) transport paths. When used as a cathode material for lithium-ion batteries, the LFP@NC nanocomposite (88.4 wt % of LiFePO4) exhibits a favorable rate performance and stable cycling performance.

  15. Synthesis and electrochemical capacitive properties of nitrogen-doped porous carbon micropolyhedra by direct carbonization of zeolitic imidazolate framework-11

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Fei; Li, Li; Zhang, Xiaohua, E-mail: mickyxie@hnu.edu.cn; Chen, Jinhua, E-mail: chenjinhua@hnu.edu.cn

    2015-06-15

    Highlights: • Nitrogen-doped porous carbon micropolyhedra (N-PCMPs) were prepared from ZIF-11. • The activated N-PCMPs with fused KOH (N-PCMPs-A) have high specific surface area. • N-PCMPs-A exhibits high specific capacitance. • N-PCMPs-A reveals good cycling performance even at a high current density. - Abstract: Nitrogen-doped porous carbon micropolyhedra (N-PCMPs) were successfully prepared by direct carbonization of ZIF-11 polyhedra and further activated with fused KOH to obtain N-PCMPs-A. The morphology and microstructure of samples were examined by scanning electron microscopy, X-ray diffraction, and micropore and chemisorption analyzer. Electrochemical properties were characterized by cyclic voltammetry and galvanostatic charge/discharge method in 1.0 M H{sub 2}SO{sub 4} aqueous solution on a standard three-electrode system. Results show that, compared with N-PCMPs, N-PCMPs-A has higher specific surface area (2188 m{sup 2} g{sup −1}) and exhibits improved electrochemical capacitive properties (307 F g{sup −1} at 1.0 A g{sup −1}). The mass specific capacitance of N-PCMPs-A is also higher than that of most MOF-derived carbons, some carbide-derived carbons and carbon aerogel-derived carbons. In addition, the capacitance of the N-PCMPs-A retains 90% after 4000 cycles even at a high current density of 10 A g{sup −1}. These imply that N-PCMPs-A is the promising materials for the construction of a high-performance supercapacitor.

  16. Nitrogen deposition: how important is it for global terrestrial carbon uptake?

    Directory of Open Access Journals (Sweden)

    G. Bala

    2013-07-01

    Full Text Available Global carbon budget studies indicate that the terrestrial ecosystems have remained a~large sink for carbon despite widespread deforestation activities. CO2-fertilization, N deposition and re-growth of mid-latitude forests are believed to be key drivers for land carbon uptake. In this study, we assess the importance of N deposition by performing idealized near-equilibrium simulations using the Community Land Model 4.0 (CLM4. In our equilibrium simulations, only 12–17% of the deposited Nitrogen is assimilated into the ecosystem and the corresponding carbon uptake can be inferred from a C : N ratio of 20:1. We calculate the sensitivity of the terrestrial biosphere for CO2-fertilization, climate warming and N deposition as changes in total ecosystem carbon for unit changes in global mean atmospheric CO2 concentration, global mean temperature and Tera grams of Nitrogen deposition per year, respectively. Based on these sensitivities, it is estimated that about 242 PgC could have been taken up by land due to the CO2 fertilization effect and an additional 175 PgC taken up as a result of the increased N deposition since the pre-industrial period. Because of climate warming, terrestrial ecosystem could have lost about 152 PgC during the same period. Therefore, since preindustrial times terrestrial carbon losses due to warming may have been approximately compensated by effects of increased N deposition, whereas the effect of CO2-fertilization is approximately indicative of the current increase in terrestrial carbon stock. Our simulations also suggest that the sensitivity of carbon storage to increased N deposition decreases beyond current levels, indicating climate warming effects on carbon storage may overwhelm N deposition effects in the future.

  17. Nitrogen deposition: how important is it for global terrestrial carbon uptake?

    Science.gov (United States)

    Bala, G.; Devaraju, N.; Chaturvedi, R. K.; Caldeira, K.; Nemani, R.

    2013-11-01

    Global carbon budget studies indicate that the terrestrial ecosystems have remained a large sink for carbon despite widespread deforestation activities. CO2 fertilization, N deposition and re-growth of mid-latitude forests are believed to be key drivers for land carbon uptake. In this study, we assess the importance of N deposition by performing idealized near-equilibrium simulations using the Community Land Model 4.0 (CLM4). In our equilibrium simulations, only 12-17% of the deposited nitrogen is assimilated into the ecosystem and the corresponding carbon uptake can be inferred from a C : N ratio of 20 : 1. We calculate the sensitivity of the terrestrial biosphere for CO2 fertilization, climate warming and N deposition as changes in total ecosystem carbon for unit changes in global mean atmospheric CO2 concentration, global mean temperature and Tera grams of nitrogen deposition per year, respectively. Based on these sensitivities, it is estimated that about 242 PgC could have been taken up by land due to the CO2 fertilization effect and an additional 175 PgC taken up as a result of the increased N deposition since the pre-industrial period. Because of climate warming, the terrestrial ecosystem could have lost about 152 PgC during the same period. Therefore, since pre-industrial times terrestrial carbon losses due to warming may have been more or less compensated by effects of increased N deposition, whereas the effect of CO2 fertilization is approximately indicative of the current increase in terrestrial carbon stock. Our simulations also suggest that the sensitivity of carbon storage to increased N deposition decreases beyond current levels, indicating that climate warming effects on carbon storage may overwhelm N deposition effects in the future.

  18. Nitrogen Controls on Climate Model Evapotranspiration.

    Science.gov (United States)

    Dickinson, Robert E.; Berry, Joseph A.; Bonan, Gordon B.; Collatz, G. James; Field, Christopher B.; Fung, Inez Y.; Goulden, Michael; Hoffmann, William A.; Jackson, Robert B.; Myneni, Ranga; Sellers, Piers J.; Shaikh, Muhammad

    2002-02-01

    Most evapotranspiration over land occurs through vegetation. The fraction of net radiation balanced by evapotranspiration depends on stomatal controls. Stomates transpire water for the leaf to assimilate carbon, depending on the canopy carbon demand, and on root uptake, if it is limiting. Canopy carbon demand in turn depends on the balancing between visible photon-driven and enzyme-driven steps in the leaf carbon physiology. The enzyme-driven component is here represented by a Rubisco-related nitrogen reservoir that interacts with plant-soil nitrogen cycling and other components of a climate model. Previous canopy carbon models included in GCMs have assumed either fixed leaf nitrogen, that is, prescribed photosynthetic capacities, or an optimization between leaf nitrogen and light levels so that in either case stomatal conductance varied only with light levels and temperature.A nitrogen model is coupled to a previously derived but here modified carbon model and includes, besides the enzyme reservoir, additional plant stores for leaf structure and roots. It also includes organic and mineral reservoirs in the soil; the latter are generated, exchanged, and lost by biological fixation, deposition and fertilization, mineralization, nitrification, root uptake, denitrification, and leaching. The root nutrient uptake model is a novel and simple, but rigorous, treatment of soil transport and root physiological uptake. The other soil components are largely derived from previously published parameterizations and global budget constraints.The feasibility of applying the derived biogeochemical cycling model to climate model calculations of evapotranspiration is demonstrated through its incorporation in the Biosphere-Atmosphere Transfer Scheme land model and a 17-yr Atmospheric Model Inter comparison Project II integration with the NCAR CCM3 GCM. The derived global budgets show land net primary production (NPP), fine root carbon, and various aspects of the nitrogen cycling are

  19. Tracking Nonpoint Source Nitrogen and Carbon in Watersheds of Chesapeake Bay

    Science.gov (United States)

    Kaushal, S.; Pennino, M. J.; Duan, S.; Blomquist, J.

    2012-12-01

    Humans have altered nitrogen and carbon cycles in rivers regionally with important impacts on coastal ecosystems. Nonpoint source nitrogen pollution is a leading contributor to coastal eutrophication and hypoxia. Shifts in sources of carbon impact downstream ecosystem metabolism and fate and transport of contaminants in coastal zones. We used a combination of stable isotopes and optical tracers to investigate fate and transport of nitrogen and carbon sources in tributaries of the largest estuary in the U.S., the Chesapeake Bay. We analyzed isotopic composition of water samples from major tributaries including the Potomac River, Susquehanna River, Patuxent River, and Choptank River during routine and storm event sampling over multiple years. A positive correlation between δ15N-NO3- and δ18O-NO3- in the Potomac River above Washington D.C. suggested denitrification or biological uptake in the watershed was removing agriculturally-derived N during summer months. In contrast, the Patuxent River in Maryland showed elevated δ15N-NO3- (5 - 12 per mil) with no relationship to δ18O-NO3- suggesting the importance of wastewater sources. From the perspective of carbon sources, there were distinct isotopic values of the δ13C-POM of particulate organic matter and fluorescence excitation emission matrices (EEMS) for rivers influenced by their dominant watershed land use. EEMS showed that there were increases in the humic and fulvic fractions of dissolved organic matter during spring floods, particularly in the Potomac River. Stable isotopic values of δ13C-POM also showed rapid depletion suggesting terrestrial carbon "pulses" in the Potomac River each spring. The δ15N-POM peaked to 10 - 15 per mil each spring suggested a potential manure source or result of biological processing within the watershed. Overall, there were considerable changes in sources and transformations of nitrogen and carbon that varied across rivers and that contribute to nitrogen and carbon loads

  20. Effect of powdered activated carbon technology on short-cut nitrogen removal for coal gasification wastewater.

    Science.gov (United States)

    Zhao, Qian; Han, Hongjun; Xu, Chunyan; Zhuang, Haifeng; Fang, Fang; Zhang, Linghan

    2013-08-01

    A combined process consisting of a powdered activated carbon technology (PACT) and short-cut biological nitrogen removal reactor (SBNR) was developed to enhance the removal efficiency of the total nitrogen (TN) from the effluent of an upflow anaerobic sludge bed (UASB) reactor, which was used to treat coal gasification wastewater (CGW). The SBNR performance was improved with the increasing of COD and TP removal efficiency via PACT. The average removal efficiencies of COD and TP in PACT were respectively 85.80% and 90.30%. Meanwhile, the NH3-N to NO2-N conversion rate was achieved 86.89% in SBNR and the total nitrogen (TN) removal efficiency was 75.54%. In contrast, the AOB in SBNR was significantly inhibited without PACT or with poor performance of PACT in advance, which rendered the removal of TN. Furthermore, PAC was demonstrated to remove some refractory compounds, which therefore improved the biodegradability of the coal gasification wastewater.

  1. A Combined System for Biological Removal of Nitrogen and Carbon from Nylon-6 Production Wastewater

    Institute of Scientific and Technical Information of China (English)

    LIU Fang; LIU Guo-hua; TIAN Qing; ZHANG Man; CHEN Ji-hua

    2007-01-01

    A combined system consisting of hydrolysisacidification, denitrification and nitrification reactors wasused to remove carbon and nitrogen from the nylon - 6production wastewater, which was characterized by goodbiodegradability and high nitrogen concentration. Theinfluences of Chemical Oxygen Demand(COD) in theinfluent, recirculation ratio, Hydraulic Residence Time(HRT) and Dissolved Oxygen(DO) concentration on thesystem performances were investigated. From results itcould be seen that good performances have been achievedduring the overall experiments periods, and COD, TotalNitrogen(TN), NH+-N and Suspended Solids(SS) in theeffluent were 53, 16, 2 and 24 mg·L-1, respectively,which has satisfied the first standard of wastewaterdischarge established by Environmental Protection Agency(EPA) of China. Furthermore, results showed thatoperation factors, viz. COD in the influent, recirculationratio, HRT and DO concentration, all had importantinfluences on the system performances.

  2. Carbon dynamics in subtropical forest soil. Effects of atmospheric carbon dioxide enrichment and nitrogen addition

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Juxiu X.; Zhou, Guoyi Y.; Zhang, Deqiang Q.; Duan, Honglang L.; Deng, Qi; Zhao, Liang [Chinese Academy of Sciences, Guangzhou (China). South China Botanical Garden; Xu, Zhihong H. [Griffith Univ., Nathan, Queensland (Australia). Environmental Futures Centre and School of Biomolecular and Physical Sciences

    2010-06-15

    The levels of atmospheric carbon dioxide concentration ([CO{sub 2}]) are rapidly increasing. Understanding carbon (C) dynamics in soil is important for assessing the soil C sequestration potential under elevated [CO{sub 2}]. Nitrogen (N) is often regarded as a limiting factor in the soil C sequestration under future CO{sub 2} enrichment environment. However, few studies have been carried out to examine what would happen in the subtropical or tropical areas where the ambient N deposition is high. In this study, we used open-top chambers to study the effect of elevated atmospheric [CO{sub 2}] alone and together with N addition on the soil C dynamics in the first 4 years of the treatments applied in southern China. Materials and methods Above- and below-ground C input (tree biomass) into soil, soil respiration, soil organic C, and total N as well as dissolved organic C (DOC) were measured periodically in each of the open-top chambers. Soil samples were collected randomly in each chamber from each of the soil layers (0-20, 20-40, and 40-60 cm) using a standard soil sampling tube (2.5-cm inside diameter). Soil leachates were collected at the bottom of the chamber below-ground walls in stainless steel boxes. Results and discussion The highest above- and below-ground C input into soil was found in the high CO{sub 2} and high N treatment (CN), followed by the only high N treatment (N+), the only high CO{sub 2} treatment (C+), and then the control (CK) without any CO{sub 2} enrichment or N addition. DOC in the leachates was small for all the treatments. Export of DOC played a minor role in C cycling in our experiment. Generally, soil respiration rate in the chambers followed the order: CN treatment > C + treatment > N + treatment > the control. Except for the C+ treatment, there were no significant differences in soil total N among the CN treatment, N + treatment, and the control. Overall, soil organic C (SOC) was significantly affected by the treatments (p < 0.0001). SOC

  3. Cometary origin of carbon, nitrogen, and water on the earth

    Science.gov (United States)

    Delsemme, A. H.

    1992-01-01

    In this paper, two assumptions on the origin of the earth are substantiated: (1) that the earth accreted from fine hot degassed dust particles containing no volatiles; and (2) that, after the accretion was finished, all the volatiles of the biosphere, including the atmosphere and the oceans, were brought to the earth by cometary bombardment. A temperature of more than 1000 K is deduced at the time when the dust that was going to form the earth was separated from the gas phase. This implies grains of anhydrous silicates and of reduced iron, without either water, carbon, or any labile elements, which remained in gas phase; thus, the minor bodies could not produce atmosphere or oceans. The second assumption is based on the evidence that cometary nuclei are formed in the outer space, by accumulation of frosty particles containing large amounts of ice and volatile molecules. It is shown that the icy bodies which hit the earth are more than enough to explain the whole biosphere.

  4. [Effects of carbon and nitrogen sources on 5-keto-gluconic acid production].

    Science.gov (United States)

    Tan, Zhilei; Wang, Hongcui; Wei, Yuqiao; Li, Yanyan; Zhong, Cheng; Jia, Shiru

    2014-01-01

    Gluconobacter oxydans is known to oxidize glucose to gluconic acid (GA), and subsequently, to 2-keto-gluconic acid (2KGA) and 5-keto-gluconic acid (5KGA), while 5KGA can be converted to L-(+)-tartaric acid. In order to increase the production of 5KGA, Gluconobacter oxydans HGI-1 that converts GA to 5KGA exclusively was chosen in this study, and effects of carbon sources (lactose, maltose, sucrose, amylum and glucose) and nitrogen sources (yeast extract, fish meal, corn steep liquor, soybean meal and cotton-seed meal) on 5KGA production were investigated. Results of experiment in 500 mL shake-flask show that the highest yield of 5KGA (98.20 g/L) was obtained using 100 g/L glucose as carbon source. 5KGA reached 100.20 g/L, 109.10 g/L, 99.83 g/L with yeast extract, fish meal and corn steep liquor as nitrogen source respectively, among which the optimal nitrogen source was fish meal. The yield of 5KGA by corn steep liquor is slightly lower than that by yeast extract. For the economic reason, corn steep liquor was selected as nitrogen source and scaled up to 5 L stirred-tank fermentor, and the final concentration of 5KGA reached 93.80 g/L, with its maximum volumetric productivity of 3.48 g/(L x h) and average volumetric productivity of 1.56 g/(L x h). The result obtained in this study showed that carbon and nitrogen sourses for large-scale production of 5KGA by Gluconobacter oxydans HGI-1 were glucose and corn steep liquor, respectively, and the available glucose almost completely (85.93%) into 5KGA.

  5. The effect of nutrients on carbon and nitrogen fixation by the UCYN-A-haptophyte symbiosis.

    Science.gov (United States)

    Krupke, Andreas; Mohr, Wiebke; LaRoche, Julie; Fuchs, Bernhard M; Amann, Rudolf I; Kuypers, Marcel M M

    2015-07-01

    Symbiotic relationships between phytoplankton and N2-fixing microorganisms play a crucial role in marine ecosystems. The abundant and widespread unicellular cyanobacteria group A (UCYN-A) has recently been found to live symbiotically with a haptophyte. Here, we investigated the effect of nitrogen (N), phosphorus (P), iron (Fe) and Saharan dust additions on nitrogen (N2) fixation and primary production by the UCYN-A-haptophyte association in the subtropical eastern North Atlantic Ocean using nifH expression analysis and stable isotope incubations combined with single-cell measurements. N2 fixation by UCYN-A was stimulated by the addition of Fe and Saharan dust, although this was not reflected in the nifH expression. CO2 fixation by the haptophyte was stimulated by the addition of ammonium nitrate as well as Fe and Saharan dust. Intriguingly, the single-cell analysis using nanometer scale secondary ion mass spectrometry indicates that the increased CO2 fixation by the haptophyte in treatments without added fixed N is likely an indirect result of the positive effect of Fe and/or P on UCYN-A N2 fixation and the transfer of N2-derived N to the haptophyte. Our results reveal a direct linkage between the marine carbon and nitrogen cycles that is fuelled by the atmospheric deposition of dust. The comparison of single-cell rates suggests a tight coupling of nitrogen and carbon transfer that stays balanced even under changing nutrient regimes. However, it appears that the transfer of carbon from the haptophyte to UCYN-A requires a transfer of nitrogen from UCYN-A. This tight coupling indicates an obligate symbiosis of this globally important diazotrophic association.

  6. Mechanism of the initial stages of nitrogen-doped single-walled carbon nanotube growth.

    Science.gov (United States)

    Susi, Toma; Lanzani, Giorgio; Nasibulin, Albert G; Ayala, Paola; Jiang, Tao; Bligaard, Thomas; Laasonen, Kari; Kauppinen, Esko I

    2011-06-21

    We have studied the mechanism of the initial stages of nitrogen-doped single-walled carbon nanotube growth illustrated for the case of a floating catalyst chemical vapor deposition system, which uses carbon monoxide (CO) and ammonia (NH(3)) as precursors and iron as a catalyst. We performed first-principles electronic-structure calculations, fully incorporating the effects of spin polarization and magnetic moments, to investigate the bonding and chemistry of CO, NH(3), and their fragments on a model Fe(55) icosahedral cluster. A possible dissociation path for NH(3) to atomic nitrogen and hydrogen was identified, with a reaction barrier consistent with an experimentally determined value we measured by tandem infrared and mass spectrometry. Both C-C and C-N bond formation reactions were found to be barrierless and exothermic, while a parasitic reaction of HCN formation had a barrier of over 1 eV.

  7. Determination of the geographical origin of Chinese teas based on stable carbon and nitrogen isotope ratios

    Institute of Scientific and Technical Information of China (English)

    Long ZHANG; Jia-rong PAN; Cheng ZHU

    2012-01-01

    The objective of this study was to investigate the geographical origin of Chinese teas using carbon and nitrogen stable isotope ratio technology.The results showed that inter-provincial dispersion of teas in Guangdong (GD),Guangxi (GX),Hainan (HA),Fujian (F J),Shandong (SD),Sichuan (SC),Chongqing (CQ),and Henan (HN) provinces was high,while in Zhejiang (ZJ),Hubei (HB),Yunnan (YN),and Anhui (AH) provinces,it was low.Tea samples from GD,GX,HA,and FJ provinces were clustered in one group and separated from those from AH and HB provinces.Thus,carbon and nitrogen stable isotope ratio technology could discriminate teas from among some provinces of China,but not from among others.Better separation might be obtained with a combination of isotopic ratios and other indexes,such as elemental data and organic components.

  8. Reprocessing of Ices in Turbulent Protoplanetary Disks: Carbon and Nitrogen Chemistry

    CERN Document Server

    Furuya, Kenji

    2014-01-01

    We study the influence of the turbulent transport on ice chemistry in protoplanetary disks, focusing on carbon and nitrogen bearing molecules. Chemical rate equations are solved with the diffusion term, mimicking the turbulent mixing in the vertical direction. Turbulence can bring ice-coated dust grains from the midplane to the warm irradiated disk surface, and the ice mantles are reprocessed by photoreactions, thermal desorption, and surface reactions. The upward transport decreases the abundance of methanol and ammonia ices at r < 30 AU, because warm dust temperature prohibits their reformation on grain surfaces. This reprocessing could explain the smaller abundances of carbon and nitrogen bearing molecules in cometary coma than those in low-mass protostellar envelopes. We also show the effect of mixing on the synthesis of complex organic molecules (COMs) are two ways: (1) transport of ices from the midplane to the disk surface and (2) transport of atomic hydrogen from the surface to the midplane. The fo...

  9. The influence of land use on soil organic carbon and nitrogen content and redox potential

    DEFF Research Database (Denmark)

    Kusliene, Gedrime

    2010-01-01

    The aim of the research was to evaluate organic matter status in the soil according to the organic carbon content, total and mineral nitrogen amounts, carbon to nitrogen (C:N) ratio and redox potential depending on land usage and plant spieces. Soil samples were taken from the fields under...... different farming systems (conventional and organic) as well as abandoned lands. We choose the plants of two botanical species (Poaceae and Fabaceae) in organic and conventional farming systems as well as abandoned lands. Experimental results show that the best soil organic matter status according...... to the investigated indexes is in the soils of conventional and orgaic farming systems occupied with mixtures of Poaceae and Fabaceae and the worst - in the soils of abandoned Poaceae meadowa. In the abandoned lands, Fabaceae (galega) had better influence on soil organic matter status than Poaceae....

  10. Changes in soil carbon, nitrogen and phosphorus due to land-use changes in Brazil

    Directory of Open Access Journals (Sweden)

    J. D. Groppo

    2015-02-01

    vegetation. The original vegetation soil phosphorus stocks were equal to 11, 22, and 43 kg ha−1 in the three soil depths, respectively. The soil phosphorus stocks increased in the CPS systems to 30, 50, and 63 kg ha−1, respectively, and in the pasture pair sites to 22, 47, and 68 kg ha−1, respectively. In the regional pasture survey, the soil phosphorus stocks were lower than in the native vegetation, and equal to 9 and 15 kg ha−1 at 0–10 and 0–30 depth layer. The findings of this paper illustrate that land-use changes that are currently common in Brazil alter soil concentrations, stocks and elemental ratios of carbon, nitrogen and phosphorus. These changes could have an impact on the subsequent vegetation, decreasing soil carbon, increasing nitrogen limitation, but alleviating soil phosphorus deficiency.

  11. Effect of Carbon and Nitrogen Content on Deformation and Fracture of AISI 304 Austenitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    C. Menapace

    2008-04-01

    Full Text Available The effect of small differences in the content of carbon and nitrogen on the room temperature tensile deformation and fracture behaviour of an AISI 304 stainless steel was studied. In the steel containing the lower amount of carbon and nitrogen, a higher amount of strain induced alfa’ martensite is formed, which increases strain hardening rate and both uniform and total elongation at fracture. The presence of large martensitic areas in the cross section causes strain localization at the austenite/martensite interface, which promotes the nucleation of cracks and their propagation along the interface. This results in a decrease of Ultimate Tensile Strength. Strain induced transformation slightly reduces strain rate sensitivity, as well.

  12. Synthesis of carbon-11, fluorine-18, and nitrogen-13 labeled radiotracers for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Fowler, J.S.; Wolf, A.P.

    1981-01-01

    A number of reviews, many of them recent, have appeared on various aspects of /sup 11/C, /sup 18/F and /sup 13/N-labeled radiotracers. This monograph treats the topic principally from the standpoint of synthetic organic chemistry while keeping in perspective the necessity of integrating the organic chemistry with the design and ultimate application of the radiotracer. Where possible, recent examples from the literature of organic synthesis are introduced to suggest potentially new routes which may be applied to problems in labeling organic molecules with the short-lived positron emitters, carbon-11, fluorine-18, and nitrogen-13. The literature survey of carbon-11, fluorine-18 and nitrogen-13 labeled compounds presented are of particular value to scientists working in this field. Two appendices are also included to provide supplementary general references. A subject index concludes this volume.

  13. Nutrient amendment does not increase mineralisation of sequestered carbon during incubation of a nitrogen limited mangrove soil

    KAUST Repository

    Keuskamp, Joost A.

    2013-02-01

    Mangrove forests are sites of intense carbon and nutrient cycling, which result in soil carbon sequestration on a global scale. Currently, mangrove forests receive increasing quantities of exogenous nutrients due to coastal development. The present paper quantifies the effects of nutrient loading on microbial growth rates and the mineralisation of soil organic carbon (SOC) in two mangrove soils contrasting in carbon content. An increase in SOC mineralisation rates would lead to the loss of historically sequestered carbon and an enhanced CO2 release from these mangrove soils.In an incubation experiment we enriched soils from Avicennia and Rhizophora mangrove forests bordering the Red Sea with different combinations of nitrogen, phosphorus and glucose to mimic the effects of wastewater influx. We measured microbial growth rates as well as carbon mineralisation rates in the natural situation and after enrichment. The results show that microbial growth is energy limited in both soils, with nitrogen as a secondary limitation. Nitrogen amendment increased the rate at which labile organic carbon was decomposed, while it decreased SOC mineralisation rates. Such an inhibitory effect on SOC mineralisation was not found for phosphorus enrichment.Our data confirm the negative effect of nitrogen enrichment on the mineralisation of recalcitrant carbon compounds found in other systems. Based on our results it is not to be expected that nutrient enrichment by itself will cause degradation of historically sequestered soil organic carbon in nitrogen limited mangrove forests. © 2012 Elsevier Ltd.

  14. Study on nitrogen doped carbon atom chains with negative differential resistance effect

    Science.gov (United States)

    Shen, Ji-Mei; Liu, Jing; Min, Yi; Zhou, Li-Ping

    2016-05-01

    Recent calculations (Mahmoud and Lugli, 2013, [21]) of gold leads sandwiching carbon chains which are separated by diphenyl-dimethyl demonstrated that the negative differential resistance (NDR) effect appears only for ;odd; numbers of carbon atoms. In this paper, according to a first-principles study based on non-equilibrium Green's function combining density functional theory, we find that the NDR effect appears both for ;odd; and for ;even; numbers of carbon atoms when the chains are doped by nitrogen atom. Our calculations remove the restriction of ;odd/even; chains for the NDR effect, which may promise the potential applications of carbon chains in the nano-scale or molecular devices in the future.

  15. Fuzzy Control of Nitrate Recirculation and External Carbon Addition in A/O Nitrogen Removal Process

    Institute of Scientific and Technical Information of China (English)

    马勇; 彭永臻; 王淑莹; 王晓莲

    2005-01-01

    Nitrogen and phosphorous concentrations of effluent water must be taken into account for the design and operation of wastewater treatment plants. In addition, the requirement for effluent quality is becoming strict.Therefore, intelligent control approaches are recently required in removing biological nutrient. In this study, fuzzy control has been successfully applied to improve the nitrogen removal. Experimental results showed that a close relationship between nitrate concentration and oxidation-reduction potential (ORP) at the end of anoxic zone was found for anoxic/oxic (A/O) nitrogen removal process treating synthetic wastewater. ORP can be used as online fuzzy control parazneter of nitrate recirculation and external carbon addition. The established fuzzy logic controller that includes two inputs and one output can maintain ORP value at-86 mV and -90 mV by adjusting the nitrate recirculation flow and external carbon dosage respectively to realize the optimal control of nitrogen removal, improving the effluent quality and reducing the operating cost.

  16. Changes of the electronic structure of the atoms of nitrogen in nitrogen-doped multiwalled carbon nanotubes under the influence of pulsed ion radiation

    Energy Technology Data Exchange (ETDEWEB)

    Korusenko, P.M., E-mail: korusenko@obisp.oscsbras.ru [Omsk Scientific Centre, Siberian Branch, Russian Academy of Sciences, Karl Marx Avenue, 15, Omsk 644024 (Russian Federation); Bolotov, V.V.; Nesov, S.N.; Povoroznyuk, S.N. [Omsk Scientific Centre, Siberian Branch, Russian Academy of Sciences, Karl Marx Avenue, 15, Omsk 644024 (Russian Federation); Khailov, I.P. [Tomsk Polytechnic University, Lenin Ave. 2a, Tomsk 634028 (Russian Federation)

    2015-09-01

    With the use of X-ray photoelectron spectroscopy (XPS) there have been investigated the changes of the chemical state of nitrogen atoms in the structure of nitrogen-doped multiwalled carbon nanotubes (CN{sub x}-MWCNTs) resulting from the impact of pulsed ion beam at various parameters of the beam (energy density, number of pulses). It has been established that irradiation with the pulsed ion beam leads to a reduction of the total amount of nitrogen in CN{sub x} nanotubes. It has been shown that a single pulse irradiation of ion beam at the energy densities of 0.5, 1, 1.5 J/cm{sup 2} leads to restructuring of the nitrogen from pyridinic and pyrrolic configuration to graphitic state. Complete removal of nitrogen (pyridinic, pyrrolic, graphitic) embedded in the structure of the walls of CN{sub x} nanotubes occurs at ten pulses and 1.5 J/cm{sup 2}.

  17. Hybrid Quantum Device with Nitrogen-Vacancy Centers in Diamond Coupled to Carbon Nanotubes

    Science.gov (United States)

    Li, Peng-Bo; Xiang, Ze-Liang; Rabl, Peter; Nori, Franco

    2016-07-01

    We show that nitrogen-vacancy (NV) centers in diamond interfaced with a suspended carbon nanotube carrying a dc current can facilitate a spin-nanomechanical hybrid device. We demonstrate that strong magnetomechanical interactions between a single NV spin and the vibrational mode of the suspended nanotube can be engineered and dynamically tuned by external control over the system parameters. This spin-nanomechanical setup with strong, intrinsic, and tunable magnetomechanical couplings allows for the construction of hybrid quantum devices with NV centers and carbon-based nanostructures, as well as phonon-mediated quantum information processing with spin qubits.

  18. ADSORPTION ISOTHERMS AND POTENTIAL DISTRIBUTIONS OF NITROGEN ON VARIOUS ACTIVATED CARBONS

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The adsorption isotherms of four activated carbons (Norit RB1, Chemviron BPL, Monolit, and Ambersorb-572) have been examined by nitrogen adsorption at 77.5 K. A method for adsorption potential distribution calculation has been proposed based on the adsorption isotherms. This distribution provides information about possible changes in the Gibbs free energy caused by the energetic and geometrical heterogeneities of an activated carbon as well as by the adsorbate-related entropic effects. The general character of the adsorption potential distribution is clearly visible by its simple relation to the micropore and mesopore distribution.

  19. Bonding preference of carbon, nitrogen, and oxygen in niobium-based rock-salt structures.

    Science.gov (United States)

    Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro; Wada, Satoshi; Magome, Eisuke; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

    2013-09-03

    Carbon, nitrogen, and oxygen are essential components in solid-state materials. However, understanding their preference on the bonding to metals has not been straightforward. Here, niobium carbide, nitride, and oxide with simple rock-salt-based structures were analyzed by first-principles calculations and synchrotron X-ray diffraction. We found that an increase in the atomic number from carbon to oxygen formed fewer and shorter bonds to metals with better hybridization of atomic orbitals. This can provide a simple guiding principle for understanding the bonding and designing carbides, nitrides, oxides, and mixed-anion compounds.

  20. Nitrogen--sulfur--carbon nanocomposites and their application as cathode materials in lithium--sulfur batteries

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng; Sun, Xiao-Guang; Guo, Bingkun; Wang, Xiqing; Mayes, Richard T.; Ben, Teng; Qiu, Shilun

    2016-09-27

    The invention is directed in a first aspect to electron-conducting porous compositions comprising an organic polymer matrix doped with nitrogen atoms and having elemental sulfur dispersed therein, particularly such compositions having an ordered framework structure. The invention is also directed to composites of such S/N-doped electron-conducting porous aromatic framework (PAF) compositions, or composites of an S/N-doped mesoporous carbon composition, which includes the S/N-doped composition in admixture with a binder, and optionally, conductive carbon. The invention is further directed to cathodes for a lithium-sulfur battery in which such composites are incorporated.

  1. Raman spectra of nitrogen-doped tetrahedral amorphous carbon from first principles

    Institute of Scientific and Technical Information of China (English)

    NIU Li; ZHU JiaQi; GAO Wei; HAN Xiao; DU ShanYi

    2009-01-01

    The non-resonant vibrational Raman spectra of nitrogen-doped tetrahedral amorphous carbon have been calculated from first principles, including the generation of s structural model, and the calculation of vibrational frequencies, vibrational eigenmodes and Raman coupling tensors. The calculated Raman spectra are in good agreement with the experimental results. The broad band at around 500 cm~(-1) arises from mixed bonds. The T peak originates from the vibrations of sp~3 carbon and the G peak comes from the stretching vibrations of sp~2-type bonding of C=C and C=N. The simulation results indicate the direct contribution of N vibrations to Raman spectra.

  2. Cement Pastes and Mortars Containing Nitrogen-Doped and Oxygen-Functionalized Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Mauricio Martínez-Alanis

    2016-01-01

    Full Text Available Cement pastes and mortars based on ordinary Portland cement containing nitrogen-doped multiwalled carbon nanotubes (MWCNT-Nx or oxygen-functionalized multiwalled carbon nanotubes (MWCNT-Ox are investigated. To incorporate MWCNTs into the cementitious matrix, the as-produced carpets are dispersed over periods of 1 and 2 hours in distilled water at pH levels of 1 and 7. The cement pastes are prepared by adding 0.1 wt% of MWCNTs to cement powder, followed by characterization with SEM and X-ray diffraction (XRD at an early age (first hours of hydration. The mortars are mechanically characterized during the hydration process for a period of 28 days. SEM characterization of cement pastes revealed that the carbon nanotubes are well incorporated in the cementitious matrix, with the hydrated cement grains interconnected by long carbon nanotubes. XRD characterizations demonstrated that, during the hydration of cement pastes, different peaks emerged that were associated with ettringite, hydrated calcium silicate, and calcium hydroxide, among other structures. Results of the compressive strength measurements for mortars simultaneously mixed with MWCNT-Nx and MWCNT-Ox reached an increment of approximately 30% in compressive strength. In addition, density functional theory calculations were performed in nitrogen-doped and oxygen-functionalized carbon nanotubes interacting with a cement grain.

  3. Soil carbon quality and nitrogen fertilization structure bacterial communities with predictable responses of major bacterial phyla

    OpenAIRE

    2014-01-01

    Agricultural practices affect the soil ecosystem in multiple ways and the soil microbial communities represent an integrated and dynamic measure of soil status. Our aim was to test whether the soil bacterial community and the relative abundance of major bacterial phyla responded predictably to long-term organic amendments representing different carbon qualities (peat and straw) in combination with nitrogen fertilization levels and if certain bacterial groups were indicative of specific treatm...

  4. Biotransformation of Meloxicam by Cunninghamella blakesleeana: Significance of Carbon and Nitrogen Source

    OpenAIRE

    Shyam Prasad, Gurram; Narasimha Rao, Kollu; Preethi, Rama; Girisham, Sivasri; S. M. Reddy

    2011-01-01

    Influence of carbon and nitrogen source, on biotransformation of meloxicam was studied by employing Cunninghamella blakesleeana NCIM 687 with an aim to achieve maximum transformation of meloxicam and in search of new metabolites. The transformation was confirmed by HPLC and based on LC–MS–MS data and previous reports the metabolites were predicted as 5-hydroxymethyl meloxicam, 5-carboxy meloxicam and a novel metabolite. The quantification of metabolites was performed using HPLC peak areas. Th...

  5. Influence of advective bio-irrigation on carbon and nitrogen cycling in sandy sediments

    OpenAIRE

    Na, T.; Gribsholt, B.; Galaktionov, O. S.; T. Lee; Meysman, F. J. R.

    2008-01-01

    In sandy sediments, the burrow ventilation activity of benthic macrofauna can generate substantial advective flows within the sediment surrounding their burrows. Here we investigated the effects of such advective bio-irrigation on carbon and nitrogen cycling in sandy sediments. To this end, we combined a range of complementary experimental and modelling approaches in a microcosm study of the lugworm Arenicola marina (Polychaeta: Annelida). Bio-irrigation rates were determined using uranine as...

  6. Fate of microbial nitrogen, carbon, hydrolysable amino acids, monosaccharides, and fatty acids in sediment

    OpenAIRE

    Veuger, Bart; van Oevelen, Dick; Middelburg, Jack J.

    2012-01-01

    The fate of microbial carbon, nitrogen, hydrolysable amino acids (HAAs), monosaccharides, and fatty acids in sediment was investigated experimentally. The microbial community of a tidal flat sediment was labeled with C-13-enriched glucose and N-15-enriched ammonium, and sediment was incubated for up to 371 days. Analysis of total concentrations and C-13- and N-15 content of bulk sediment, hydrolysable amino acids (including D-alanine), monosaccharides, total fatty acids (TFAs), and phospholip...

  7. Enhancement of Photocatalytic Activity on TiO2-Nitrogen-Doped Carbon Nanotubes Nanocomposites

    OpenAIRE

    Lingling Wang; Long Shen; Yihuai Li; Luping Zhu; Jiaowen Shen; Lijun Wang

    2013-01-01

    TiO2-nitrogen-doped carbon nanotubes (TiO2-CNx) nanocomposites are successfully synthesized via a facile hydrothermal method. The prepared photocatalysts were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric and differential scanning calorimetry analyses (TGA-DSC). The results show that the TiO2 nanoparticles with a narrow size of 7 nm are uniformly deposited on CNx. The photocatalytic ac...

  8. Growth of metal-catalyst-free nitrogen-doped metallic single-wall carbon nanotubes

    Science.gov (United States)

    Li, Jin-Cheng; Hou, Peng-Xiang; Zhang, Lili; Liu, Chang; Cheng, Hui-Ming

    2014-09-01

    Nitrogen-doped (N-doped) single-wall carbon nanotubes (SWCNTs) were synthesized by chemical vapor deposition using SiOx nanoparticles as a catalyst and ethylenediamine as the source of both carbon and nitrogen. The N-doped SWCNTs have a mean diameter of 1.1 nm and a narrow diameter range, with 92% of them having diameters from 0.7 to 1.4 nm. Multi-wavelength laser Raman spectra and temperature-dependent electrical resistance indicate that the SWCNT sample is enriched with metallic nanotubes. These N-doped SWCNTs showed excellent electrocatalytic activity for the oxygen reduction reaction and highly selective and sensitive sensing ability for dopamine detection.Nitrogen-doped (N-doped) single-wall carbon nanotubes (SWCNTs) were synthesized by chemical vapor deposition using SiOx nanoparticles as a catalyst and ethylenediamine as the source of both carbon and nitrogen. The N-doped SWCNTs have a mean diameter of 1.1 nm and a narrow diameter range, with 92% of them having diameters from 0.7 to 1.4 nm. Multi-wavelength laser Raman spectra and temperature-dependent electrical resistance indicate that the SWCNT sample is enriched with metallic nanotubes. These N-doped SWCNTs showed excellent electrocatalytic activity for the oxygen reduction reaction and highly selective and sensitive sensing ability for dopamine detection. Electronic supplementary information (ESI) available: Additional information including Raman spectra, ORR polarization curves, CV curves, etc. See DOI: 10.1039/c4nr03172e

  9. Nitrogen-Doped Carbon as a Cathode Material for Lithium-air Batteries (Postprint)

    Science.gov (United States)

    2010-04-01

    Handbook of Batteries and Fuel Cells, D. Linden , Editor, Chapter 38, Mc-Graw-Hil, New York (1984). [3] J. Read, J. Electrochem. Soc., 153, (2006) A96...MATERIAL FOR LITHIUM-AIR BATTERIES (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62203F 6. AUTHOR( S ...AFRL-RQ-WP-TP-2015-0050 NITROGEN-DOPED CARBON AS A CATHODE MATERIAL FOR LITHIUM-AIR BATTERIES (POSTPRINT) Padmakar Kichambare and Stanley

  10. Short-term carbon and nitrogen cycling in urine patches assessed by combined carbon-13 and nitrogen-15 labelling

    DEFF Research Database (Denmark)

    Ambus, Per; Petersen, S.O.; Soussana, J.F.

    2007-01-01

    sources for C include the urine itself, increased solubility of soil C, lysis of microbial cells and leakage of C from scorched roots. The objective of this experiment was to test the hypothesis that: (i) urine deposition causes an increase in root-derived degradable C compounds in the soil, which (ii......Urine deposition by grazing animals is known to, induce large NO emissions as a result of increased nitrification and denitrification in the soil. This is brought about by the increased N availability from the urine, in combination very likely also with increased organic C availability. Possible...... application was equal to the quantity of organic C added. Immediately after the application, 87% of the respired CO2 appeared to be from the urine, and respiration of plant-derived C was temporarily decreased. The cumulated amount of respired C-13 plant carbon, however, was unaltered by the urine treatment...

  11. CO{sub 2} removal potential of carbons prepared by co-pyrolysis of sugar and nitrogen containing compounds

    Energy Technology Data Exchange (ETDEWEB)

    Arenillas, A.; Drage, T.C.; Smith, K.; Snape, C.E. [University of Nottingham, Fuel Science Group, School of Chemical, Environmental and Mining Engineering, University Park, Nottingham NG7 2RD (United Kingdom)

    2005-08-15

    The nitrogen enrichment of active carbons is reported to be effective in enhancing the specific adsorbate-adsorbent interactions for CO{sub 2}. In this work, nitrogen-enriched carbons were prepared by co-pyrolysis of sugar and a series of nitrogen compounds with different nitrogen functionalities. The results show that although the amount of nitrogen incorporated to the final adsorbent is important, the N-functionality seems to be more relevant for increasing CO{sub 2} uptake. Thus, the adsorbent obtained from urea co-pyrolysis presents the highest nitrogen content but the lowest CO{sub 2} adsorption capacity. However, the adsorbent obtained from carbazole co-pyrolysis, despite the lower amount of N incorporated, shows high CO{sub 2} uptake, up to 9wt.%, probably because the presence of more basic functionalities as determined by XPS analysis.

  12. Does exogenous carbon extend the realized niche of canopy lichens? Evidence from sub-boreal forests in British Columbia.

    Science.gov (United States)

    Campbell, Jocelyn; Bengtson, Per; Fredeen, Arthur L; Coxson, Darwyn S; Prescott, Cindy E

    2013-05-01

    Foliose lichens with cyanobacterial bionts (bipartite and tripartite) form a distinct assemblage of epiphytes strongly associated with humid microclimatic conditions in inland British Columbia. Previous research showed that these cyano- and cephalolichen communities are disproportionately abundant and species-rich on conifer saplings beneath Populus compared to beneath other tree species. More revealing, lichens with cyanobacterial bionts were observed beneath Populus even in stands that did not otherwise support them. We experimentally test the hypothesis that this association is due to the interception of glucose-rich nectar that is exuded from Populus extra-floral nectaries (EFN). Using CO2 flux measurements and phospholipid fatty acid (PLFA) analysis with experimental applications of 13C6-labeled glucose, we demonstrate that cyano- and cephalolichens have a strong respiratory response to glucose. Lichens treated with glucose had lower net photosynthesis and higher establishment rates than control thalli. Furthermore, lichens with cyanobacterial bionts rapidly incorporate exogenous 13C into lichen fatty acid tissues. A large proportion of the 13C taken up by the lichens was incorporated into fungal biomarkers, suggesting that the mycobiont absorbed and assimilated the majority of applied 13C6 glucose. Our observations suggest that both cyanolichens and cephalolichens may utilize an exogenous source of glucose, made available by poplar EFNs. The exogenous C may enable these lichens to become established by providing a source of C for fungal respiration despite drought-induced inactivity of the cyanobacterial partner. As such, the mycobiont may adopt an alternative nutritional strategy, using available exogenous carbon to extend its realized niche.

  13. EFFECTS OF ELEVATED ATMOSPHERIC CO{sub 2} ON CANOPY TRANSPIRATION IN SENESCENT SPRING WHEAT

    Energy Technology Data Exchange (ETDEWEB)

    GROSSMAN,S.; KIMBALL,B.A.; HUNSAKER,D.J.; LONG,S.P.; GARCIA,R.L.; KARTSCHALL,TH.; WALL,G.W.; PINTER,P.J,JR.; WECHSUNG,F.; LAMORTE,R.L.

    1998-12-31

    The seasonal course of canopy transpiration and the diurnal courses of latent heat flux of a spring wheat crop were simulated for atmospheric CO{sub 2} concentrations of 370 {micro}mol mol{sup {minus}1} and 550 {micro}mol mol{sup {minus}1}. The hourly weather data, soil parameters and the irrigation and fertilizer treatments of the Free-Air Carbon Dioxide Enrichment wheat experiment in Arizona (1992/93) were used to drive the model. The simulation results were tested against field measurements with special emphasis on the period between anthesis and maturity. A model integrating leaf photosynthesis and stomatal conductance was scaled to a canopy level in order to be used in the wheat growth model. The simulated intercellular CO{sub 2} concentration, C{sub i} was determined from the ratio of C{sub i} to the CO{sub 2} concentration at the leaf surface, C{sub s} the leaf to air specific humidity deficit and a possibly unfulfilled transpiration demand. After anthesis, the measured assimilation rates of the flag leaves decreased more rapidly than their stomatal conductances, leading to a rise in the C{sub i}/C{sub s} ratio. In order to describe this observation, an empirical model approach was developed which took into account the leaf nitrogen content for the calculation of the C{sub i}/C{sub s} ratio. Simulation results obtained with the new model version were in good agreement with the measurements. If changes in the C{sub i}/C{sub s} ratio accorded to the decrease in leaf nitrogen content during leaf senescence were not considered in the model, simulations revealed an underestimation of the daily canopy transpiration of up to 20% and a decrease in simulated seasonal canopy transpiration by 10%. The measured reduction in the seasonal sum of canopy transpiration and soil evaporation owing to CO{sub 2} enrichment, in comparison, was only about 5%.

  14. Influence of oxygen on nitrogen-doped carbon nanofiber growth directly on nichrome foil

    Science.gov (United States)

    Vishwakarma, Riteshkumar; Shinde, Sachin M.; Saufi Rosmi, Mohamad; Takahashi, Chisato; Papon, Remi; Mahyavanshi, Rakesh D.; Ishii, Yosuke; Kawasaki, Shinji; Kalita, Golap; Tanemura, Masaki

    2016-09-01

    The synthesis of various nitrogen-doped (N-doped) carbon nanostructures has been significantly explored as an alternative material for energy storage and metal-free catalytic applications. Here, we reveal a direct growth technique of N-doped carbon nanofibers (CNFs) on flexible nichrome (NiCr) foil using melamine as a solid precursor. Highly reactive Cr plays a critical role in the nanofiber growth process on the metal alloy foil in an atmospheric pressure chemical vapor deposition (APCVD) process. Oxidation of Cr occurs in the presence of oxygen impurities, where Ni nanoparticles are formed on the surface and assist the growth of nanofibers. Energy-dispersive x-ray spectroscopy (EDXS) and x-ray photoelectron spectroscopy (XPS) clearly show the transformation process of the NiCr foil surface with annealing in the presence of oxygen impurities. The structural change of NiCr foil assists one-dimensional (1D) CNF growth, rather than the lateral two-dimensional (2D) growth. The incorporation of distinctive graphitic and pyridinic nitrogen in the graphene lattice are observed in the synthesized nanofiber, owing to better nitrogen solubility. Our finding shows an effective approach for the synthesis of highly N-doped carbon nanostructures directly on Cr-based metal alloys for various applications.

  15. The interdependence of the reactive species of oxygen, nitrogen, and carbon.

    Science.gov (United States)

    Bild, Walther; Ciobica, Alin; Padurariu, Manuela; Bild, Veronica

    2013-03-01

    This mini-review tries to summarize the main interdependences between the free radicals of oxygen, nitrogen, and carbon. Also, the main metabolic pathways for these radical species are described, as well as how these affect their interaction and functional implications. Emphasis is made on the metabolic disturbances induced by stressing aggressions that produce radical species. In this way, cellular oxidative imbalances created by the superiority of reactive oxygen species over the antioxidant systems produce both activation of nitroxide synthases and the oxidation of terminal nitrogen from L-arginine, as well as the metabolization of heme until carbon monoxide by nitric oxide-activated hemoxygenase. Also, multiple cellular protein and nucleoprotein alterations determined by these three kinds of radical species are completed by the involvement of hydrogen sulfide, which results from the degradation of L-cysteine by cistationine-γ-lyase. In this way, sufficient experimental data tend to demonstrate the involvement of hydrogen sulfide and other thiol derivatives in the interrelations between oxygen, nitrogen, and carbon, which results in a true radical cascade. Thus, oxidative stress, together with nitrosative and carbonilic stress, may constitute a central point where other factors of vulnerability meet, and their interactions could have an important impact in many modern diseases. Considering that the actions of reactive species can be most of the time corrected, future studies need to establish the therapeutical importance of various agents which modulate oxidative, nitrosative, or carbonilic stress.

  16. Effects of bimetallic catalysts on synthesis of nitrogen-doped carbon nanotubes as nanoscale energetic materials

    Institute of Scientific and Technical Information of China (English)

    Hao Liu; Yong Zhang; Ruying Li; Xueliang Sun; Hakima Abou-Rachid

    2011-01-01

    Well aligned nitrogen-doped carbon nanotubes (CNx-NTs),as energetic materials,are synthesized on a silicon substrate by aerosol-assisted chemical vapor deposition.Tungsten (W) and molybdenum (Mo) metals are respectively introduced to combine with iron (Fe) to act as a bimetallic co-catalyst layer.Correlations between the composition and shape of the co-catalyst and morphology,size,growth rate and nitrogen doping amount of the synthesized CNx-NTs are investigated by secondary and backscattered electron imaging in a field emission scanning electron microscope (FESEM) and X-ray photoelectron spectrometer (XPS).Compared to pure iron catalyst.W-Fe co-catalyst can result in lower growth rate,larger diameter and wider size distribution of the CNx-NTs; while incorporation of molybdenum into the iron catalyst layer can reduce the diameter and size distribution of the nanotubes.Compared to the sole iron catalyst,Fe-W catalyst impedes nitrogen doping while Fe-Mo catalyst promotes the incorporation of nitrogen into the nanotubes.The present work indicates that CNx-NTs with modulated size,growth rate and nitrogen doping concentration are expected to be synthesized by tuning the size and composition of co-catalysts,which may find great potential in producing CNx-NTs with controlled structure and properties.

  17. Carbon dioxide level and form of soil nitrogen regulate assimilation of atmospheric ammonia in young trees.

    Science.gov (United States)

    Silva, Lucas C R; Salamanca-Jimenez, Alveiro; Doane, Timothy A; Horwath, William R

    2015-08-21

    The influence of carbon dioxide (CO2) and soil fertility on the physiological performance of plants has been extensively studied, but their combined effect is notoriously difficult to predict. Using Coffea arabica as a model tree species, we observed an additive effect on growth, by which aboveground productivity was highest under elevated CO2 and ammonium fertilization, while nitrate fertilization favored greater belowground biomass allocation regardless of CO2 concentration. A pulse of labelled gases ((13)CO2 and (15)NH3) was administered to these trees as a means to determine the legacy effect of CO2 level and soil nitrogen form on foliar gas uptake and translocation. Surprisingly, trees with the largest aboveground biomass assimilated significantly less NH3 than the smaller trees. This was partly explained by declines in stomatal conductance in plants grown under elevated CO2. However, unlike the (13)CO2 pulse, assimilation and transport of the (15)NH3 pulse to shoots and roots varied as a function of interactions between stomatal conductance and direct plant response to the form of soil nitrogen, observed as differences in tissue nitrogen content and biomass allocation. Nitrogen form is therefore an intrinsic component of physiological responses to atmospheric change, including assimilation of gaseous nitrogen as influenced by plant growth history.

  18. Synthesis of High-Surface-Area Nitrogen-Doped Porous Carbon Microflowers and Their Efficient Carbon Dioxide Capture Performance.

    Science.gov (United States)

    Li, Yao; Cao, Minhua

    2015-07-01

    Sustainable carbon materials have received particular attention in CO2 capture and storage owing to their abundant pore structures and controllable pore parameters. Here, we report high-surface-area hierarchically porous N-doped carbon microflowers, which were assembled from porous nanosheets by a three-step route: soft-template-assisted self-assembly, thermal decomposition, and KOH activation. The hydrazine hydrate used in our experiment serves as not only a nitrogen source, but also a structure-directing agent. The activation process was carried out under low (KOH/carbon=2), mild (KOH/carbon=4) and severe (KOH/carbon=6) activation conditions. The mild activated N-doped carbon microflowers (A-NCF-4) have a hierarchically porous structure, high specific surface area (2309 m(2)  g(-1)), desirable micropore size below 1 nm, and importantly large micropore volume (0.95 cm(3)  g(-1)). The remarkably high CO2 adsorption capacities of 6.52 and 19.32 mmol g(-1) were achieved with this sample at 0 °C (273 K) and two pressures, 1 bar and 20 bar, respectively. Furthermore, this sample also exhibits excellent stability during cyclic operations and good separation selectivity for CO2 over N2.

  19. Impact of carbon on the surface and activity of silica-carbon supported copper catalysts for reduction of nitrogen oxides

    Science.gov (United States)

    Spassova, I.; Stoeva, N.; Nickolov, R.; Atanasova, G.; Khristova, M.

    2016-04-01

    Composite catalysts, prepared by one or more active components supported on a support are of interest because of the possible interaction between the catalytic components and the support materials. The supports of combined hydrophilic-hydrophobic type may influence how these materials maintain an active phase and as a result a possible cooperation between active components and the support material could occur and affects the catalytic behavior. Silica-carbon nanocomposites were prepared by sol-gel, using different in specific surface areas and porous texture carbon materials. Catalysts were obtained after copper deposition on these composites. The nanocomposites and the catalysts were characterized by nitrogen adsorption, TG, XRD, TEM- HRTEM, H2-TPR, and XPS. The nature of the carbon predetermines the composite's texture. The IEPs of carbon materials and silica is a force of composites formation and determines the respective distribution of the silica and carbon components on the surface of the composites. Copper deposition over the investigated silica-carbon composites leads to formation of active phases in which copper is in different oxidation states. The reduction of NO with CO proceeds by different paths on different catalysts due to the textural differences of the composites, maintaining different surface composition and oxidation states of copper.

  20. The effects of chronic nitrogen fertilization on alpine tundra soil microbial communities: implications for carbon and nitrogen cycling.

    Science.gov (United States)

    Nemergut, Diana R; Townsend, Alan R; Sattin, Sarah R; Freeman, Kristen R; Fierer, Noah; Neff, Jason C; Bowman, William D; Schadt, Christopher W; Weintraub, Michael N; Schmidt, Steven K

    2008-11-01

    Many studies have shown that changes in nitrogen (N) availability affect primary productivity in a variety of terrestrial systems, but less is known about the effects of the changing N cycle on soil organic matter (SOM) decomposition. We used a variety of techniques to examine the effects of chronic N amendments on SOM chemistry and microbial community structure and function in an alpine tundra soil. We collected surface soil (0-5 cm) samples from five control and five long-term N-amended plots established and maintained at the Niwot Ridge Long-term Ecological Research (LTER) site. Samples were bulked by treatment and all analyses were conducted on composite samples. The fungal community shifted in response to N amendments, with a decrease in the relative abundance of basidiomycetes. Bacterial community composition also shifted in the fertilized soil, with increases in the relative abundance of sequences related to the Bacteroidetes and Gemmatimonadetes, and decreases in the relative abundance of the Verrucomicrobia. We did not uncover any bacterial sequences that were closely related to known nitrifiers in either soil, but sequences related to archaeal nitrifiers were found in control soils. The ratio of fungi to bacteria did not change in the N-amended soils, but the ratio of archaea to bacteria dropped from 20% to less than 1% in the N-amended plots. Comparisons of aliphatic and aromatic carbon compounds, two broad categories of soil carbon compounds, revealed no between treatment differences. However, G-lignins were found in higher relative abundance in the fertilized soils, while proteins were detected in lower relative abundance. Finally, the activities of two soil enzymes involved in N cycling changed in response to chronic N amendments. These results suggest that chronic N fertilization induces significant shifts in soil carbon dynamics that correspond to shifts in microbial community structure and function.

  1. Advanced low carbon-to-nitrogen ratio wastewater treatment by electrochemical and biological coupling process.

    Science.gov (United States)

    Deng, Shihai; Li, Desheng; Yang, Xue; Zhu, Shanbin; Xing, Wei

    2016-03-01

    Nitrogen pollution in ground and surface water significantly affects the environment and its organisms, thereby leading to an increasingly serious environmental problem. Such pollution is difficult to degrade because of the lack of carbon sources. Therefore, an electrochemical and biological coupling process (EBCP) was developed with a composite catalytic biological carrier (CCBC) and applied in a pilot-scale cylindrical reactor to treat wastewater with a carbon-to-nitrogen (C/N) ratio of 2. The startup process, coupling principle, and dynamic feature of the EBCP were examined along with the effects of hydraulic retention time (HRT), dissolved oxygen (DO), and initial pH on nitrogen removal. A stable coupling system was obtained after 51 days when plenty of biofilms were cultivated on the CCBC without inoculation sludge. Autotrophic denitrification, with [Fe(2+)] and [H] produced by iron-carbon galvanic cells in CCBC as electron donors, was confirmed by equity calculation of CODCr and nitrogen removal. Nitrogen removal efficiency was significantly influenced by HRT, DO, and initial pH with optimal values of 3.5 h, 3.5 ± 0.1 mg L(-1), and 7.5 ± 0.1, respectively. The ammonia, nitrate, and total nitrogen (TN) removal efficiencies of 90.1 to 95.3 %, 90.5 to 99.0 %, and 90.3 to 96.5 % were maintained with corresponding initial concentrations of 40 ± 2 mg L(-1) (NH3-N load of 0.27 ± 0.01 kg NH3-N m(-3) d(-1)), 20 ± 1 mg L(-1), and 60 ± 2 mg L(-1) (TN load of 0.41 ± 0.02 kg TN m(-3) d(-1)). Based on the Eckenfelder model, the kinetics equation of the nitrogen transformation along the reactor was N e  = N 0 exp (-0.04368 h/L(1.8438)). Hence, EBCP is a viable method for advanced low C/N ratio wastewater treatment.

  2. Carbon, nitrogen and pH regulate the production and activity of a polygalacturonase isozyme produced by Penicillium expansum

    Science.gov (United States)

    The influence of carbon, nitrogen and pH on polygalacturonase activity produced by Penicillium expansum were investigated. P. expansum mycelial growth was greatest on lyophilized fruit tissue and the highest PG activity occurred in apple pectin medium. Nitrogen source influenced PG activity and was ...

  3. Carbon and Nitrogen Use Efficiency in Microbial Communities in Antarctic Soils

    Science.gov (United States)

    Prommer, Judith; Spohn, Marie; Klaus, Karoline; Kusch, Stephanie; Wanek, Wolfgang; Dercon, Gerd; Richter, Andreas

    2016-04-01

    Terrestrial ecosystems in the Antarctic experience harsh environmental conditions including very low temperatures and a low carbon input leading to poorly developed ecosystems with low diversity and a low soil organic matter content, which may be vulnerable to perturbations in a future climate. Microbial transformation and decomposition of soil organic matter under the extreme climatic conditions in the Antarctic has received little attention so far. Specifically, little is known about microbial process rates and how they might be affected by climate warming. We here report on C and N transformation rates and their corresponding microbial use efficiencies in two soil horizons of two sites on King George Island, the maritime Antarctica. We used novel isotope techniques to estimate microbial carbon use efficiency (CUE; based on incorporation of 18O from water into DNA) and nitrogen use efficiency (NUE; based on a 15N isotope pool dilution assays). The investigated two contrasting sites at marine terraces on basaltic rocks that were characterized by a stable surface. While both sites were similar in exposition, distance from sea and elevation, they differed in their vegetation cover and several biogeochemical parameters, such as soil pH and soil organic carbon and nitrogen content. Surprisingly, we found low soil C:N ratios at both sites and for both horizons, i.e. below 12 in the organic crust and below 8 in the first mineral horizon. This indicates a low carbon availability relative to nitrogen and would thus imply a high microbial CUE. However, our results showed also a low CUE at both sites and in both horizons (CUE of 24% and 9% in the organic crust and mineral layer, respectively). In contrast, NUE was very high in organic layers (98%), pointing towards a strong nitrogen limitation, while in the mineral horizons, NUE was lower (between 84% and 72%), as expected for soil horizons with a C:N ratio below 8. Thus, the NUE pattern followed stoichiometric theory (i

  4. Mesoporous Nitrogen-Doped Carbon-Glass Ceramic Cathodes for Solid-State Lithium-Oxygen Batteries (Postprint)

    Science.gov (United States)

    2012-01-01

    A. C.; Swanson, S .; Wilcke, W. J. Phys. Chem. Lett. 2010, 1, 2193−2203. (3) In Handbook of Batteries and Fuel Cells, 2nd ed.; Linden , D., Ed...AFRL-RZ-WP-TP-2012-0057 MESOPOROUS NITROGEN-DOPED CARBON-GLASS CERAMIC CATHODES FOR SOLID-STATE LITHIUM−OXYGEN BATTERIES (Postprint...November 2011 4. TITLE AND SUBTITLE MESOPOROUS NITROGEN-DOPED CARBON-GLASS CERAMIC CATHODES FOR SOLID-STATE LITHIUM−OXYGEN BATTERIES (Postprint

  5. Reassessing carbon sequestration in the North China Plain via addition of nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Wenxu, E-mail: dongwx@sjziam.ac.cn [Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021 (China); Duan, Yongmei, E-mail: 106086193@QQ.com [Geological Survey of Jiangxi Province, Nanchang 330030 (China); Wang, Yuying, E-mail: wangyy@sjziam.ac.cn [Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021 (China); Hu, Chunsheng, E-mail: cshu@sjziam.ac.cn [Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021 (China)

    2016-09-01

    Soil inorganic carbon (SIC) exerts a strong influence on the carbon (C) sequestered in response to nitrogen (N) additions in arid and semi-arid ecosystems, but limited information is available on in situ SIC storage and dissolution at the field level. This study determined the soil organic/inorganic carbon storage in the soil profile at 0–100 cm depths and the concentration of dissolved inorganic carbon (DIC) in soil leachate in 4 N application treatments (0, 200, 400, and 600 kg N ha{sup −1} yr{sup −1}) for 15 years in the North China Plain. The objectives were to evaluate the effect of nitrogen fertilizer on total amount of carbon sequestration and the uptake of atmospheric CO{sub 2} in an agricultural system. Results showed that after 15 years of N fertilizer application the SOC contents at depths of 0–100 cm significantly increased, whereas the SIC contents significantly decreased at depths of 0–60 cm. However, the actual measured loss of carbonate was far higher than the theoretical maximum values of dissolution via protons from nitrification. Furthermore, the amount of HCO{sub 3}{sup −} and the HCO{sub 3}{sup −} / (Ca{sup 2+} + Mg{sup 2+}) ratio in soil leachate were higher in the N application treatments than no fertilizer input (CK) for the 0–80 cm depth. The result suggested that the dissolution of carbonate was mainly enhanced by soil carbonic acid, a process which can absorb soil or atmosphere CO{sub 2} and less influenced by protons through the nitrification which would release CO{sub 2}. To accurately evaluate soil C sequestration under N input scenarios in semi-arid regions, future studies should include both changes in SIC storage as well as the fractions of dissolution with different sources of acids in soil profiles. - Highlights: • The SOC contents significantly increased after long-term nitrogen application, while SIC decreased. • The measured loss of carbonate was far higher than the theoretical values of dissolution from

  6. A natural light/dark cycle regulation of carbon-nitrogen metabolism and gene expression in rice shoots

    Directory of Open Access Journals (Sweden)

    Haixing Li

    2016-08-01

    Full Text Available Light and temperature are two particularly important environmental cues for plant survival. Carbon and nitrogen are two essential macronutrients required for plant growth and development, and cellular carbon and nitrogen metabolism must be tightly coordinated. In order to understand how the natural light/dark cycle regulates carbon and nitrogen metabolism in rice plants, we analyzed the photosynthesis, key carbon-nitrogen metabolites and enzyme activities, and differentially expressed genes and miRNAs involved in the carbon and nitrogen metabolic pathway in rice shoots at the following times: 2:00, 6:00, 10:00, 14:00, 18:00 and 22:00. Our results indicated that more CO2 was fixed into carbohydrates by a high net photosynthetic rate, respiratory rate and stomatal conductance in the daytime. Although high levels of the nitrate reductase activity, free ammonium and carbohydrates were exhibited in the daytime, the protein synthesis was not significantly facilitated by the light and temperature. In mRNA sequencing, the carbon and nitrogen metabolism-related differentially expressed genes were obtained, which could be divided into eight groups: photosynthesis, TCA cycle, sugar transport, sugar metabolism, nitrogen transport, nitrogen reduction, amino acid metabolism and nitrogen regulation. Additionally, a total of 78,306 alternative splicing events have been identified, which primarily belong to alternative 5' donor sites, alternative 3' acceptor sites, intron retention and exon skipping. In sRNA sequencing, four carbon and nitrogen metabolism-related miRNAs (osa-miR1440b, osa-miR2876-5p, osa-miR1877 and osa-miR5799 were determined to be regulated by natural light/dark cycle. The expression level analysis showed that the four carbon and nitrogen metabolism-related miRNAs negatively regulated their target genes. These results may provide a good strategy to study how natural light/dark cycle regulates carbon and nitrogen metabolism to ensure plant

  7. Effects of carbon and nitrogen sources on fatty acid contents and composition in the green microalga, Chlorella sp. 227.

    Science.gov (United States)

    Cho, Sunja; Lee, Dukhaeng; Luong, Thao Thanh; Park, Sora; Oh, You-Kwan; Lee, Taeho

    2011-10-01

    In order to investigate and generalize the effects of carbon and nitrogen sources on the growth of and lipid production in Chlorella sp. 227, several nutritional combinations consisting of different carbon and nitrogen sources and concentrations were given to the media for cultivation of Chlorella sp. 227, respectively. The growth rate and lipid content were affected largely by concentration rather than by sources. The maximum specific growth was negatively affected by low concentrations of carbon and nitrogen. There is a maximum allowable inorganic carbon concentration (less than 500~1,000 mM bicarbonate) in autotrophic culture, but the maximum lipid content per gram dry cell weight (g DCW) was little affected by the concentration of inorganic carbon within the concentration. The lipid content per g DCW was increased when the microalga was cultured with the addition of glucose and bicarbonate (mixotrophic) at a fixed nitrogen concentration and with the lowest nitrogen concentration (0.2 mM), relatively. Considering that lipid contents per g DCW increased in those conditions, it suggests that a high ratio of carbon to nitrogen in culture media promotes lipid accumulation in the cells. Interestingly, a significant increase of the oleic acid amount to total fatty acids was observed in those conditions. These results showed the possibility to induce lipid production of high quality and content per g DCW by modifying the cultivation conditions.

  8. First-principles study of palladium atom adsorption on the boron- or nitrogen-doped carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Chen Guoxiang [College of Physics and Information Technology, Shaanxi Normal University, Xi' an 710062, Shaanxi (China); School of Science, Xi' an Shiyou University, Xi' an 710065, Shaanxi (China); Zhang Jianmin, E-mail: jianm_zhang@yahoo.co [College of Physics and Information Technology, Shaanxi Normal University, Xi' an 710062, Shaanxi (China); Wang Doudou [Institute of Telecommunication Engineering of the Air Force Engineering University (AFEU1), Xi' an 710077, Shaanxi (China); Xu Kewei [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049, Shaanxi (China)

    2009-11-15

    We have performed first-principles calculation to investigate the adsorption of a single palladium atom on the surface of the pristine and boron- or nitrogen-doped carbon nanotubes (CNTs). The results show that for the adsorption of a single palladium atom on the pristine CNT surface, the most stable site is Bridge1 site above the axial carbon-carbon bond. Either boron- or nitrogen-doped CNTs can assist palladium surface adsorption, but the detailed mechanisms are different. The enhanced palladium adsorption on boron-doped CNT is attributed to the palladium d orbital strongly hybridized with both boron p orbital and carbon p orbital. The enhancement in palladium adsorption on nitrogen-doped CNT results from activating the nitrogen-neighboring carbon atoms due to the large electron affinity of nitrogen. Furthermore, the axial bond is preferred over the zigzag bond for a palladium atom adsorbed on the surface of all three types of CNTs. The most energetically favorable site for a palladium atom adsorbed on three types of CNTs is above the axial boron-carbon bond in boron-doped CNT. The enhancement in palladium adsorption is more significant for the boron-doped CNT than it is for nitrogen-doped CNT with a similar configuration. So we conclude that accordingly, the preferred adsorption site is determined by the competition between the electron affinity of doped and adsorbed atoms and preferred degree of the axial bond over the zigzag bond.

  9. Global terrestrial carbon and nitrogen cycling insensitive to estimates of biological N fixation

    Science.gov (United States)

    Steinkamp, J.; Weber, B.; Werner, C.; Hickler, T.

    2015-12-01

    Dinitrogen (N2) is the most abundant molecule in the atmosphere and incorporated in other molecules an essential nutrient for life on earth. However, only few natural processes can initiate a reaction of N2. These natural processes are fire, lightning and biological nitrogen fixation (BNF) with BNF being the largest source. In the course of the last century humans have outperformed the natural processes of nitrogen fixation by the production of fertilizer. Industrial and other human emission of reactive nitrogen, as well as fire and lightning lead to a deposition of 63 Tg (N) per year. This is twice the amount of BNF estimated by the default setup of the dynamic global vegetation model LPJ-GUESS (30 Tg), which is a conservative approach. We use different methods and parameterizations for BNF in LPJ-GUESS: 1.) varying total annual amount; 2.) annual evenly distributed and daily calculated fixation rates; 3.) an improved dataset of BNF by cryptogamic covers (free-living N-fixers). With this setup BNF is ranging from 30 Tg to 60 Tg. We assess the impact of BNF on carbon storage and grand primary production (GPP) of the natural vegetation. These results are compared to and evaluated against available independent datasets. We do not see major differences in the productivity and carbon stocks with these BNF estimates, suggesting that natural vegetation is insensitive to BNF on a global scale and the vegetation can compensate for the different nitrogen availabilities. Current deposition of nitrogen compounds and internal cycling through mineralization and uptake is sufficient for natural vegetation productivity. However, due to the coarse model grid and spatial heterogeneity in the real world this conclusion does not exclude the existence of habitats constrained by BNF.

  10. Phenol Adsorption on Nitrogen-enriched Activated Carbon Prepared from Bamboo Residues

    Directory of Open Access Journals (Sweden)

    Ji Zhang

    2013-12-01

    Full Text Available Nitrogen-enriched activated carbons prepared from bamboo residues were characterized by means of BET, XPS, and elemental analysis. Then adsorption experiments were carried out to study the effects of various physicochemical parameters such as contact time, temperature, pH, and initial concentration. Adsorption equilibrium was achieved within 120 min at a phenol concentration of 250 mg/L. When the pH was 4 and 0.1 g of the carbon absorbent and 100 mL of phenol solution at 250 mg/L were used, the phenol adsorption of the ACs with melamine and urea modifications were 219.09 mg/g and 214.45 mg/g, respectively. Both were greater than the capacity of unmodified AC, which was 163.82 mg/g. The Langmuir isotherm adsorption equation well described the experimental adsorption isotherms. The adsorption kinetics was well explained by pseudo-second-order kinetics rather than the pseudo-first-order. In conclusion, the nitrogen-enriched activated carbon proposed as adsorbents of the phenol wastewater were shown to be effective, which also means that bamboo residues have promise as activated carbon precursors for liquid phase adsorbents for environmental protection.

  11. Simulated effects of nitrogen saturation on the global carbon budget using the IBIS model

    Science.gov (United States)

    Lu, Xuehe; Jiang, Hong; Liu, Jinxun; Zhang, Xiuying; Jin, Jiaxin; Zhu, Qiuan; Zhang, Zhen; Peng, Changhui

    2016-12-01

    Over the past 100 years, human activity has greatly changed the rate of atmospheric N (nitrogen) deposition in terrestrial ecosystems, resulting in N saturation in some regions of the world. The contribution of N saturation to the global carbon budget remains uncertain due to the complicated nature of C-N (carbon-nitrogen) interactions and diverse geography. Although N deposition is included in most terrestrial ecosystem models, the effect of N saturation is frequently overlooked. In this study, the IBIS (Integrated BIosphere Simulator) was used to simulate the global-scale effects of N saturation during the period 1961–2009. The results of this model indicate that N saturation reduced global NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) by 0.26 and 0.03 Pg C yr‑1, respectively. The negative effects of N saturation on carbon sequestration occurred primarily in temperate forests and grasslands. In response to elevated CO2 levels, global N turnover slowed due to increased biomass growth, resulting in a decline in soil mineral N. These changes in N cycling reduced the impact of N saturation on the global carbon budget. However, elevated N deposition in certain regions may further alter N saturation and C-N coupling.

  12. Simulated effects of nitrogen saturation the global carbon budget using the IBIS model

    Science.gov (United States)

    Lu, Xuehe; Jiang, Hong; Liu, Jinxun; Zhang, Xiuying; Jin, Jiaxin; Zhu, Qiuan; Zhang, Zhen; Peng, Changhui

    2016-01-01

    Over the past 100 years, human activity has greatly changed the rate of atmospheric N (nitrogen) deposition in terrestrial ecosystems, resulting in N saturation in some regions of the world. The contribution of N saturation to the global carbon budget remains uncertain due to the complicated nature of C-N (carbon-nitrogen) interactions and diverse geography. Although N deposition is included in most terrestrial ecosystem models, the effect of N saturation is frequently overlooked. In this study, the IBIS (Integrated BIosphere Simulator) was used to simulate the global-scale effects of N saturation during the period 1961–2009. The results of this model indicate that N saturation reduced global NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) by 0.26 and 0.03 Pg C yr−1, respectively. The negative effects of N saturation on carbon sequestration occurred primarily in temperate forests and grasslands. In response to elevated CO2 levels, global N turnover slowed due to increased biomass growth, resulting in a decline in soil mineral N. These changes in N cycling reduced the impact of N saturation on the global carbon budget. However, elevated N deposition in certain regions may further alter N saturation and C-N coupling.

  13. Manganese oxide nanowires wrapped with nitrogen doped carbon layers for high performance supercapacitors.

    Science.gov (United States)

    Li, Ying; Mei, Yuan; Zhang, Lin-Qun; Wang, Jian-Hai; Liu, An-Ran; Zhang, Yuan-Jian; Liu, Song-Qin

    2015-10-01

    In this study, manganese oxide nanowires wrapped by nitrogen-doped carbon layers (MnO(x)@NCs) were prepared by carbonization of poly(o-phenylenediamine) layer coated onto MnO2 nanowires for high performance supercapacitors. The component and structure of the MnO(x)@NCs were controlled through carbonization procedure under different temperatures. Results demonstrated that this composite combined the high conductivity and high specific surface area of nitrogen-doped carbon layers with the high pseudo-capacitance of manganese oxide nanowires. The as-prepared MnO(x)@NCs exhibited superior capacitive properties in 1 M Na2SO4 aqueous solution, such as high conductivity (4.167×10(-3) S cm(-1)), high specific capacitance (269 F g(-1) at 10 mV s(-1)) and long cycle life (134 F g(-1) after 1200 cycles at a scan rate of 50 mV s(-1)). It is reckoned that the present novel hybrid nanowires can serve as a promising electrode material for supercapacitors and other electrochemical devices.

  14. Patterns of dissolved organic carbon and nitrogen fluxes in deciduous and coniferous forests under historic high nitrogen deposition

    Science.gov (United States)

    Sleutel, S.; Vandenbruwane, J.; de Schrijver, A.; Wuyts, K.; Moeskops, B.; Verheyen, K.; de Neve, S.

    2009-12-01

    Numerous recent studies have indicated that dissolved organic carbon (DOC) and nitrogen (DON) play an important role in C and N cycling in natural ecosystems, and have shown that N deposition alters the concentrations and fluxes of dissolved organic substances and may increase leaching losses from forests. Our study was set up to accurately quantify concentrations and flux patterns of DOC, DON and dissolved inorganic nitrogen (DIN) in deciduous and coniferous forest in Flanders, Belgium, under historical high nitrogen deposition. We measured DOC, DON and DIN concentrations at two weekly intervals in a silver birch (SB) stand, a corsican pine (CP) stand and a pine stand with higher N deposition (CPN), and used the SWAP model (calibrated with PEST) for generating accurate water and matter fluxes. The input with precipitation was an important source of DON, but not for DOC. Release of DOC from the forest floor was minimally affected by forest type, but higher N deposition (CPN stand) caused an 82% increase of DOC release from the forest floor. Adsorption to mineral soil material rich in iron and/or aluminum oxyhydroxides was suggested to be the most important process removing DOC from the soil solution, responsible for substantial retention (67-84%) of DOC entering the mineral soil profile with forest floor leachate. Generally, DON was less reactive (i.e. less removal from the soil solution) than DOC, resulting in decreasing DOC/DON ratios with soil depth. We found increased DOC retention in the mineral soil as a result of higher N deposition (84 kg ha-1 yr-1 additional DOC retention in CPN compared to CP). Overall DON leaching losses were 2.2, 3.3 and 5.0 kg N yr-1 for SB, CP and CPN, respectively, contributing between 9-28% to total dissolved N (TDN) leaching. The relative contribution to TDN leaching from DON loss from SB and CP was mainly determined by (large) differences in DIN leaching. The large TDN leaching losses are alarming, especially in the CPN stand that

  15. Patterns of dissolved organic carbon (DOC) and nitrogen (DON) fluxes in deciduous and coniferous forests under historic high nitrogen deposition

    Science.gov (United States)

    Sleutel, S.; Vandenbruwane, J.; de Schrijver, A.; Wuyts, K.; Moeskops, B.; Verheyen, K.; de Neve, S.

    2009-07-01

    Numerous recent studies have indicated that dissolved organic carbon (DOC) and nitrogen (DON) play an important role in C and N cycling in natural ecosystems, and have shown that N deposition alters the concentrations and fluxes of dissolved organic substances and may increase leaching losses from forests. Our study was set up to accurately quantify concentrations and flux patterns of DOC, DON and dissolved inorganic nitrogen (DIN) in deciduous and coniferous forest in Flanders under historical high nitrogen deposition. We measured DOC, DON and DIN concentrations at two weekly intervals in a silver birch (SB) stand, a corsican pine (CP) stand and a pine stand with higher N deposition (CPN), and used the SWAP model (calibrated with PEST) for generating accurate water and matter fluxes. The input with precipitation was an important source of DON, but not for DOC. Release of DOC from the forest floor was minimally affected by forest type, but higher N deposition (CPN stand) caused an 82% increase of DOC release from the forest floor. Adsorption to mineral soil material rich in iron and/or aluminum oxyhydroxides was suggested to be the most important process removing DOC from the soil solution, responsible for substantial retention (67-84%) of DOC entering the mineral soil profile with forest floor leachate. Generally, DON was less reactive (i.e. less removal from the soil solution) than DOC, resulting in decreasing DOC/DON ratios with soil depth. We found increased DOC retention in the mineral soil as a result of higher N deposition (84 kg N ha-1 yr-1 additional DOC retention in CPN compared to CP). Overall DON leaching losses were 2.2, 3.3 and 5.0 kg N ha-1 yr-1 for SB, CP and CPN, respectively, contributing between 9-28% to total dissolved N (TDN) leaching. DON loss from SB and CP was not much higher than from unpolluted forests, and its relative contribution to TDN leaching was mainly determined by (large) differences in DIN leaching. The large TDN leaching losses

  16. Patterns of dissolved organic carbon (DOC and nitrogen (DON fluxes in deciduous and coniferous forests under historic high nitrogen deposition

    Directory of Open Access Journals (Sweden)

    S. Sleutel

    2009-07-01

    Full Text Available Numerous recent studies have indicated that dissolved organic carbon (DOC and nitrogen (DON play an important role in C and N cycling in natural ecosystems, and have shown that N deposition alters the concentrations and fluxes of dissolved organic substances and may increase leaching losses from forests. Our study was set up to accurately quantify concentrations and flux patterns of DOC, DON and dissolved inorganic nitrogen (DIN in deciduous and coniferous forest in Flanders under historical high nitrogen deposition. We measured DOC, DON and DIN concentrations at two weekly intervals in a silver birch (SB stand, a corsican pine (CP stand and a pine stand with higher N deposition (CPN, and used the SWAP model (calibrated with PEST for generating accurate water and matter fluxes. The input with precipitation was an important source of DON, but not for DOC. Release of DOC from the forest floor was minimally affected by forest type, but higher N deposition (CPN stand caused an 82% increase of DOC release from the forest floor. Adsorption to mineral soil material rich in iron and/or aluminum oxyhydroxides was suggested to be the most important process removing DOC from the soil solution, responsible for substantial retention (67–84% of DOC entering the mineral soil profile with forest floor leachate. Generally, DON was less reactive (i.e. less removal from the soil solution than DOC, resulting in decreasing DOC/DON ratios with soil depth. We found increased DOC retention in the mineral soil as a result of higher N deposition (84 kg N ha−1 yr−1 additional DOC retention in CPN compared to CP. Overall DON leaching losses were 2.2, 3.3 and 5.0 kg N ha−1 yr−1 for SB, CP and CPN, respectively, contributing between 9–28% to total dissolved N (TDN leaching. DON loss from SB and CP was not much higher than from unpolluted forests, and its relative contribution to TDN leaching was mainly determined by

  17. Patterns of dissolved organic carbon and nitrogen fluxes in deciduous and coniferous forests under historic high nitrogen deposition

    Directory of Open Access Journals (Sweden)

    S. Sleutel

    2009-12-01

    Full Text Available Numerous recent studies have indicated that dissolved organic carbon (DOC and nitrogen (DON play an important role in C and N cycling in natural ecosystems, and have shown that N deposition alters the concentrations and fluxes of dissolved organic substances and may increase leaching losses from forests. Our study was set up to accurately quantify concentrations and flux patterns of DOC, DON and dissolved inorganic nitrogen (DIN in deciduous and coniferous forest in Flanders, Belgium, under historical high nitrogen deposition. We measured DOC, DON and DIN concentrations at two weekly intervals in a silver birch (SB stand, a corsican pine (CP stand and a pine stand with higher N deposition (CPN, and used the SWAP model (calibrated with PEST for generating accurate water and matter fluxes. The input with precipitation was an important source of DON, but not for DOC. Release of DOC from the forest floor was minimally affected by forest type, but higher N deposition (CPN stand caused an 82% increase of DOC release from the forest floor. Adsorption to mineral soil material rich in iron and/or aluminum oxyhydroxides was suggested to be the most important process removing DOC from the soil solution, responsible for substantial retention (67–84% of DOC entering the mineral soil profile with forest floor leachate. Generally, DON was less reactive (i.e. less removal from the soil solution than DOC, resulting in decreasing DOC/DON ratios with soil depth. We found increased DOC retention in the mineral soil as a result of higher N deposition (84 kg ha−1 yr−1 additional DOC retention in CPN compared to CP. Overall DON leaching losses were 2.2, 3.3 and 5.0 kg N yr−1 for SB, CP and CPN, respectively, contributing between 9–28% to total dissolved N (TDN leaching. The relative contribution to TDN leaching from DON loss from SB and CP was mainly determined by (large differences in DIN leaching. The large TDN leaching

  18. Effect of Nitrogen and Hydrogen Gases on the Synthesis of Carbon Nanomaterials from Coal Waste Fly Ash as a Catalyst.

    Science.gov (United States)

    Hintsho, Nomso; Shaikjee, Ahmed; Triphati, Pranav K; Masenda, Hilary; Naidoo, Deena; Franklyn, Paul; Durbach, Shane

    2016-05-01

    Various reducing and inert gases have been used in the catalytic chemical vapour deposition (CCVD) synthesis of carbon nanomaterials (CNMs). In this paper we report on the effects that hydrogen and nitrogen gases have on the production of CNMs from acetylene on fly ash catalysts. Parameters such as temperature and gas environments were investigated. Transmission electron microscopy (TEM) revealed that CNMs of various morphologies such as carbon nanofibers (CNFs) and carbon nanospheres (CNSs) were formed. When hydrogen was used the carbonaceous products were formed in higher yields as compared to when nitrogen was used. This could be due to the multifunctional roles that hydrogen plays as compared to nitrogen. Laser Raman and Mössbauer spectroscopy measurements revealed that three types of products were formed, namely: amorphous carbon, graphitic carbon and iron carbide. Significantly cementite (Fe3C) was identified as the main intermediate carbide species in the catalytic growth of well-ordered CNMs.

  19. Environmental impacts of coastal fish farming; Carbon and Nitrogen budgets for trout farming in Kaldbacksfjord, Faroe Islands

    DEFF Research Database (Denmark)

    Nordi, Gunnvor A; Glud, Ronnie N.; Gaard, Eilif;

    2011-01-01

    Flow of organic carbon (OC) and nitrogen through a sea cage trout farm was calculated on the basis of detailed studies of the farming operation, water circulation, OC and nutrient transport and recycling processes in sediment. A third of the OC and nitrogen provided by fish food was incorporated...... with increasing food input; the divergence between carbon efflux and oxygen uptake in sediment likewise increased with increasing food input, reflecting an increasing level of sediment reduction. Directly below the farm, the dissolved organic carbon (DOC) efflux was high (on average 53% of dissolved inorganic...... carbon efflux), indicating that DOC efflux is an important pathway for benthic carbon release below aquaculture farms. Overall, microbial processes removed 56 and 38% of OC and nitrogen, respectively, that settled to the seabed. During a 39 d break in farming activity, due to the combined effect...

  20. Variation in foliar respiration and wood CO2 efflux rates among species and canopy layers in a wet tropical forest.

    Science.gov (United States)

    Asao, Shinichi; Bedoya-Arrieta, Ricardo; Ryan, Michael G

    2015-02-01

    As tropical forests respond to environmental change, autotrophic respiration may consume a greater proportion of carbon fixed in photosynthesis at the expense of growth, potentially turning the forests into a carbon source. Predicting such a response requires that we measure and place autotrophic respiration in a complete carbon budget, but extrapolating measurements of autotrophic respiration from chambers to ecosystem remains a challenge. High plant species diversity and complex canopy structure may cause respiration rates to vary and measurements that do not account for this complexity may introduce bias in extrapolation more detrimental than uncertainty. Using experimental plantations of four native tree species with two canopy layers, we examined whether species and canopy layers vary in foliar respiration and wood CO2 efflux and whether the variation relates to commonly used scalars of mass, nitrogen (N), photosynthetic capacity and wood size. Foliar respiration rate varied threefold between canopy layers, ∼0.74 μmol m(-2) s(-1) in the overstory and ∼0.25 μmol m(-2) s(-1) in the understory, but little among species. Leaf mass per area, N and photosynthetic capacity explained some of the variation, but height explained more. Chamber measurements of foliar respiration thus can be extrapolated to the canopy with rates and leaf area specific to each canopy layer or height class. If area-based rates are sampled across canopy layers, the area-based rate may be regressed against leaf mass per area to derive the slope (per mass rate) to extrapolate to the canopy using the total leaf mass. Wood CO2 efflux varied 1.0-1.6 μmol m(-2) s(-1) for overstory trees and 0.6-0.9 μmol m(-2) s(-1) for understory species. The variation in wood CO2 efflux rate was mostly related to wood size, and little to species, canopy layer or height. Mean wood CO2 efflux rate per surface area, derived by regressing CO2 efflux per mass against the ratio of surface

  1. Modelling the carbon and nitrogen balances of direct land use changes from energy crops in Denmark

    DEFF Research Database (Denmark)

    Hamelin, Lorie; Jørgensen, Uffe; Petersen, Bjørn Molt;

    2012-01-01

    This paper addresses the conversion of Danish agricultural land from food/feed crops to energy crops. To this end, a life cycle inventory, which relates the input and output flows from and to the environment of 528 different crop systems, is built and described. This includes seven crops (annuals......- and micronutrients are presented. The inventory results highlight Miscanthus as a promising energy crop, indicating it presents the lowest emissions of nitrogen compounds, the highest amount of carbon dioxide sequestrated from the atmosphere, a relatively high carbon turnover efficiency and allows to increase soil...... organic carbon. Results also show that the magnitude of these benefits depends on the harvest season, soil types and climatic conditions. Inventory results further highlight winter wheat as the only annual crop where straw removal for bioenergy may be sustainable, being the only annual crop not involving...

  2. Nitrogen doped carbon nanoparticles enhanced extracellular electron transfer for high-performance microbial fuel cells anode.

    Science.gov (United States)

    Yu, Yang-Yang; Guo, Chun Xian; Yong, Yang-Chun; Li, Chang Ming; Song, Hao

    2015-12-01

    Nitrogen doped carbon nanoparticles (NDCN) were applied to modify the carbon cloth anodes of microbial fuel cells (MFCs) inoculated with Shewanella oneidensis MR-1, one of the most well-studied exoelectrogens. Experimental results demonstrated that the use of NDCN increased anodic absorption of flavins (i.e., the soluble electron mediator secreted by S. oneidensis MR-1), facilitating shuttle-mediated extracellular electron transfer. In addition, we also found that NDCN enabled enhanced contact-based direct electron transfer via outer-membrane c-type cytochromes. Taken together, the performance of MFCs with the NDCN-modified anode was enormously enhanced, delivering a maximum power density 3.5 times' higher than that of the MFCs without the modification of carbon cloth anodes.

  3. BOREAS TE-9 NSA Canopy Biochemistry

    Science.gov (United States)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Margolis, Hank; Charest, Martin; Sy, Mikailou

    2000-01-01

    The BOREAS TE-9 team collected several data sets related to chemical and photosynthetic properties of leaves. This data set contains canopy biochemistry data collected in 1994 in the NSA at the YJP, OJR, OBS, UBS, and OA sites, including biochemistry lignin, nitrogen, cellulose, starch, and fiber concentrations. These data were collected to study the spatial and temporal changes in the canopy biochemistry of boreal forest cover types and how a high-resolution radiative transfer model in the mid-infrared could be applied in an effort to obtain better estimates of canopy biochemical properties using remote sensing. The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  4. Facile synthesis of reduced graphene oxide-modified, nitrogen-doped carbon xerogel with enhanced electrochemical capacitance

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Gang [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Hu, Xiaoyong [College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Peng, Zhiguang [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Hu, Jiawen, E-mail: jwhu@hnu.edu.cn [College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Liu, Hongtao, E-mail: liuht@csu.edu.cn [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China)

    2014-12-15

    In this contribution, we report a reduced graphene oxide (rGO)-modified nitrogen-doped carbon xerogel, which could be easily prepared by pyrolysis of melamine-formaldehyde (MF) resins that are polymerized hydrothermally in an aqueous GO dispersion. Scanning electron microscopy, transmission electron microscopy, Fourier-transformed infrared spectrometry, and nitrogen adsorption-desorption method were employed to reveal the morphologies and structures of the prepared carbon xerogel. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge were used to investigate the electrochemical properties. The results showed that the charge transfer barrier of the mesoporous nitrogen-doped carbon xerogel was decreased evidently, owing to the modification of a layer of rGO on its wall, and the xerogel demonstrated a capacitance of as high as 205 F g{sup −1} at the current of 1 A g{sup −1}. - Graphical abstract: A facile synthesis of rGO-modified, N-doped carbon material for supercapacitor application. - Highlights: • Nitrogen-doping and graphene-attachment in the carbon material are simultaneously achieved. • A thin layer of graphene attached on the wall of the mesoporous carbon material speeds up the charge transfer. • The graphene-modified nitrogen-doped carbon xerogel shows great potential for supercapacitor application.

  5. Isolation and characterization of a bacterium which utilizes polyester polyurethane as a sole carbon and nitrogen source.

    Science.gov (United States)

    Nakajima-Kambe, T; Onuma, F; Kimpara, N; Nakahara, T

    1995-06-01

    Various soil samples were screened for the presence of microorganisms which have the ability to degrade polyurethane compounds. Two strains with good polyurethane degrading activity were isolated. The more active strain was tentatively identified as Comamonas acidovorans. This strain could utilize polyester-type polyurethanes but not the polyether-type polyurethanes as sole carbon and nitrogen sources. Adipic acid and diethylene glycol were probably the main degradation products when polyurethane was supplied as a sole carbon and nitrogen source. When ammonium nitrate was used as nitrogen source, only diethylene glycol was detected after growth on polyurethane.

  6. Retrieving canopy leaf total nitrogen content of winter wheat by continuous wavelet transform%小波法反演条锈病胁迫下冬小麦冠层叶片全氮含量

    Institute of Scientific and Technical Information of China (English)

    何汝艳; 乔小军; 蒋金豹; 郭会敏

    2015-01-01

    The aim of this paper is to monitor the nitrogen nutrition status of winter wheat under stripe rust stress by hyperspectral remote sensing. The experiment was carried out at Beijing Xiaotangshan Precision Agriculture Experimental Base, China (40°10.6′N, 116°16.3′E). The cultivar of winter wheat was Jingdong 8 which was very susceptible to stripe rust. Canopy spectral reflectance data of winter wheat was collected by an ASD Fieldspec FR spectroradiometer and the disease index (DI) was measured through counting the number of wheat leaf under stripe rust stress artificially in the field. Leaf total nitrogen (LTN) content of winter wheat used to calculate DI was measured in the laboratory. The relationship between DI of stripe rust and LTN content of winter wheat was analyzed. The canopy spectra were processed by the method of continuous wavelet transform (CWT) on 10 scales, therefore, a series of wavelet coefficients were obtained in this way. The correlation coefficients between wavelet coefficients and LTN content were calculated, and then, the wavelet coefficients, which had strong correlation with LTN content, were chosen. Several hyperspectral indices were also selected according to previous research results, namely SR (simple ratio index), PRI (photochemical reflectance index), NDVI (normalized difference vegetation index), OSAVI (optimized soil-adjusted vegetation index), SIPI (Structure insensitive pigment index), LIC1 (lichtenthaler index 1), LIC2 (lichtenthaler index 2), LIC3 (lichtenthaler index 3), TVI (triangular vegetation index) and MTVI2 (modified triangular vegetation index 2), which had high correlations with LTN content. Both wavelet coefficients and hyperspectral indices were used as independent variables of models to retrieve LTN content of winter wheat, and support vector machine (SVM) regression method was used to establish the estimation models. The above estimation models of different types of variables were made a comparison. Cross

  7. Carbon rhizodeposition by plants of contrasting strategies for resource acquisition: responses to various nitrogen fertility regimes

    Science.gov (United States)

    Baptist, Florence; Aranjuelo, I.; Lopez-Sangil, L.; Rovia, P.; Nogués, S.

    2010-05-01

    Rhizodeposition by plants is one of the most important physiological mechanisms related to carbon and nitrogen cycling which is also believed to vary along the acquisition-conservation continuum. However, owing to methodological difficulties (i.e. narrow zone of soil around roots and rapid assimilation by soil microbes), root exudation and variations between species are one of the most poorly understood belowground process. Although previous approaches such as hydroponic culture based system, permit the chemical analysis of exudates, the fact that this protocol is qualitative, conditions its utility (see review in Phillips et al. 2008). Others techniques based on pulse-labelling approach have been developed to quantify rhizodeposition but are rarely sufficient to uniformly label all plant inputs to soil. Consequently with this typical pulse chase methods, recent assimilates are labeled but the recalcitrant carbon will not be labeled and therefore the contribution of this carbon will not be considered. Hence, traditional pulse labelling is not a quantitative means of tracing carbon due to inhomogeneous labelling and so limits greatly comparative studies of rhizodeposition fluxes at the interspecific level. In this study we developped a new protocole based on a long-term (3 months) steady state 13C labelling in order (1) to quantify rhizodeposition fluxes for six graminoid species caracterized by contrasted nutrient acquisition strategies and (2) to investigate to what extent various level of nitrogen fertility regimes modulate rhizodeposition fluxes. This method will enable to quantify under natural soil conditions both the accumulation of 13C in the soil but also the quantity that has been respired by the microorganisms during a given time and so will give an integrated picture of rhizodeposition fluxes for each species under each nitrogen fertility level. Results are currently being processed and will be presented at the conference. References: Phillips RP, Erlitz

  8. Flooding affects uptake and distribution of carbon and nitrogen in citrus seedlings.

    Science.gov (United States)

    Martínez-Alcántara, Belén; Jover, Sara; Quiñones, Ana; Forner-Giner, María Ángeles; Rodríguez-Gamir, Juan; Legaz, Francisco; Primo-Millo, Eduardo; Iglesias, Domingo J

    2012-08-15

    Soil flooding has been widely reported to affect large areas of the world. In this work, we investigated the effect of waterlogging on citrus carbon and nitrogen pools and partitioning. Influence on their uptake and translocation was also studied through ¹⁵N and ¹³C labeling to provide insight into the physiological mechanisms underlying the responses. The data indicated that flooding severely reduced photosynthetic activity and affected growth and biomass partitioning. Total nitrogen content and concentration in the plant also progressively decreased throughout the course of the experiment. After 36 days of treatment, nitrogen content of flooded plants had decreased more than 2.3-fold compared to control seedlings, and reductions in nitrogen concentration ranged from 21 to 55% (in roots and leaves, respectively). Specific absorption rate and transport were also affected, leading to important changes in the distribution of this element inside the plant. Additionally, experiments involving labeled nitrogen revealed that ¹⁵N uptake rate and accumulation were drastically decreased at the end of the experiment (93% and 54%, respectively). ¹³CO₂ assimilation into the plant was strongly reduced by flooding, with δ¹³C reductions ranging from 22 to 37% in leaves and roots, respectively. After 36 days, the relative distribution of absorbed ¹³C was also altered. Thus, ¹³C recovery in flooded leaves increased compared to controls, whereas roots exhibited the opposite pattern. Interestingly, when carbohydrate partitioning was examined, the data revealed that sucrose concentration was augmented significantly in roots (37-56%), whereas starch was reduced. In leaves, a marked increase in sucrose was detected from the first sampling onwards (36-66%), and the same patter was observed for starch. Taken together, these results indicate that flooding altered carbon and nitrogen pools and partitioning in citrus. On one hand, reduced nitrogen concentration appears to

  9. Carbon and Nitrogen Cycling in Urban Landscapes: Global, Regional Dynamics and Case Studies.

    Science.gov (United States)

    Svirejeva-Hopkins, A.; Nardoto, G. B.; Schellnhuber, H.

    2008-12-01

    The urban population has been growing rapidly in the last decades and is predicted to continue its exponential trend, especially in the developing countries, which would create additional pressure on the environment by overpopulated unsustainable cities and will continue to substantially change the main Biogeochemical cycles. Such disturbances in the main driving cycle of the Biosphere (global carbon cycle) and the nitrogen cycle, induced by sprawling urban human activities, lead to global, regional and local environmental problems, i.e. global warming, photochemical smog, stratospheric ozone depletion, soil acidification, nitrate pollution of surface and ground water, coastal ecosystem disturbances. Since urban areas are expected to continue their rapid expansion in the 21st century, accompanied by growing energy production, increased food demand, expanding transportation and industrialization it becomes more and more important to be able to describe and forecast the dynamics of biogeochemical functioning of these landscapes (which have altered characteristics compared to the natural ecosystems). Moreover, from the environmental policy perspective, a high density of people makes cities focal points of vulnerability to global environmental change. The model based on the forecasting the dynamics of urban area growth, allows us to forecast the dynamics of Carbon and Nitrogen on the urban territories at different scales. However, nitrogen cycle is very complex and is closely interlinked with the other major biogeochemical cycles, such as oxygen and water. The system of water supply and liquid waste carried by water out of the system 'city' is investigated. In order to better understand the mechanisms of cycling, we consider the case studies, when we investigated the detailed fluxes of Carbon and Nitrogen in Sao Paolo (Brazil) and Paris (France). When we know the yearly amounts of carbon and nitrogen, produced by a city, we should be capable of coming up with what

  10. Hierarchically porous carbons with optimized nitrogen doping as highly active electrocatalysts for oxygen reduction

    Science.gov (United States)

    Liang, Hai-Wei; Zhuang, Xiaodong; Brüller, Sebastian; Feng, Xinliang; Müllen, Klaus

    2014-09-01

    Development of efficient, low-cost and stable electrocatalysts as the alternative to platinum for the oxygen reduction reaction is of significance for many important electrochemical devices, such as fuel cells, metal-air batteries and chlor-alkali electrolysers. Here we report a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation. Our protocol allows for the simultaneous optimization of both porous structures and surface functionalities of nitrogen-doped carbons. Accordingly, the prepared catalysts show the highest oxygen reduction reaction activity (half-wave potential of 0.85 V versus reversible hydrogen electrode with a low loading of 0.1 mg cm-2) in alkaline media among all reported metal-free catalysts. Significantly, when used for constructing the air electrode of zinc-air battery, our metal-free catalyst outperforms the state-of the-art platinum-based catalyst.

  11. Adsorption of hydrogen in Scandium/Titanium decorated nitrogen doped carbon nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Mananghaya, Michael, E-mail: mikemananghaya@gmail.com [De La Salle University, 2401 Taft Ave, 0922, Manila (Philippines); DLSU STC Laguna Boulevard, LTI Spine Road Barangays Biñan and Malamig, Biñan City, Laguna (Philippines); DOST-ASTHRDP, PCIEERD, Gen. Santos Ave., Bicutan, Taguig City 1631 (Philippines); Belo, Lawrence Phoa; Beltran, Arnel [De La Salle University, 2401 Taft Ave, 0922, Manila (Philippines); DLSU STC Laguna Boulevard, LTI Spine Road Barangays Biñan and Malamig, Biñan City, Laguna (Philippines)

    2016-09-01

    Nitrogen doped Carbon Nanotube with divacancy (4ND-CN{sub x}NT) that is decorated with Scandium and Titanium as potential hydrogen storage medium using the pseudo potential density functional method was investigated. Highly localized states near the Fermi level, which are derived from the nitrogen defects, contribute to strong Sc and Ti bindings, which prevent metal aggregation and improve the material stability. A detailed Comparison of the Hydrogen adsorption capability with promising system-weight efficiency of Sc over Ti was elucidated when functionalized with 4ND-CN{sub x}NT. Finally, the (Sc/4ND){sub 10}-CN{sub x}CNT composite material has a thermodynamically favorable adsorption and consecutive adsorption energy for ideal reversible adsorption and desorption of hydrogen at room temperature such that it can hold at least 5.8 wt% hydrogen molecules at the LDA and GGA level. - Highlights: • Carbon Nanotube with divacancy (4ND-CN{sub x}NT) decorated with Sc and Ti. • Nitrogen defects, contribute to strong Sc and Ti bindings. • H{sub 2} and (Sc/4ND){sub 10}-CN{sub x}CNT has a favorable adsorption. • 5.8 wt% adsorption at the LDA and GGA level.

  12. Simultaneous carbon, nitrogen and phosphorous removal from municipal wastewater in a circulating fluidized bed bioreactor.

    Science.gov (United States)

    Patel, Ajay; Zhu, Jesse; Nakhla, George

    2006-11-01

    In this study, the performance of the circulating fluidized bed bioreactor (CFBB) with anoxic and aerobic beds and employing lava rock as a carrier media for the simultaneous removal of carbon, nitrogen and phosphorus from municipal wastewater at an empty bed contact time (EBCT) of 0.82 h was discussed. The CFBB was operated without and with bioparticles' recirculation between the anoxic and aerobic bed for 260 and 110 d respectively. Without particles' recirculation, the CFBB was able to achieve carbon (C), total nitrogen (N) and phosphorous (P) removal efficiencies of 94%, 80% and 65% respectively, whereas with bioparticles' recirculation, 91%, 78% and 85% removals of C, N and P were achieved. The CFBB was operated at long sludge retention time (SRT) of 45-50 d, and achieved a sludge yield of 0.12-0.135 g VSS g COD(-1). A dynamic stress study of the CFBB was carried out at varying feed flow rates and influent ammonia concentrations to determine response to shock loadings. The CFBB responded favourably in terms of TSS and COD removal to quadrupling of the feed flow rate. However, nitrification was more sensitive to hydraulic shock loadings than to doubling of influent nitrogen loading.

  13. The influence of oxidation with nitric acid on the preparation and properties of active carbon enriched in nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Pietrzak, Robert [Laboratory of Coal Chemistry and Technology, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan (Poland)], E-mail: pietrob@amu.edu.pl; Nowicki, Piotr; Wachowska, Helena [Laboratory of Coal Chemistry and Technology, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan (Poland)

    2009-01-01

    The effect of oxidation by 20% nitric acid on the properties and performance of active carbons enriched with nitrogen by means of the reaction with urea in the presence of air has been studied. The study has been made on demineralised orthocoking coal and the carbonisates obtained from it at 600 or 700 deg. C, subjected to the processes of nitrogenation, oxidation and activation with KOH in different sequences. The amount of nitrogen introduced into the carbon with the aid of urea has been found to depend on the stage at which the process of nitrogenation was performed. The process of oxidation of the demineralised coal and the active carbon obtained from the former has been found to favour nitrogen introduction into the carbon structure. In the process of nitrogenation of the carbonisates the amount of nitrogen introduced has inversely depended on the temperature of carbonisation. The modifications of the processes permitted obtaining materials of different textural parameters, different acid-base character of the surface and different iodine sorption capacity.

  14. Nitrogen-doped carbon nanotubes with tunable structure and high yield produced by ultrasonic spray pyrolysis

    Science.gov (United States)

    Liu, Jian; Zhang, Yong; Ionescu, Mihnea Ioan; Li, Ruying; Sun, Xueliang

    2011-06-01

    Nitrogen-doped carbon nanotubes (CN x) were prepared by ultrasonic spray pyrolysis from mixtures of imidazole and acetonitrile. Imidazole, as an additive, was used to control the structure and nitrogen doping in CN x by adjusting its concentration in the mixtures. Scanning electron microscopy observation showed that the addition of imidazole increased the nanotube growth rate and yield, while decreased the nanotube diameter. Transmission electron microscopy study indicated that the addition of imidazole promoted the formation of a dense bamboo-like structure in CN x. X-ray photoelectron spectroscopy analysis demonstrated that the nitrogen content varied from 3.2 to 5.2 at.% in CN x obtained with different imidazole concentrations. Raman spectra study showed that the intensity ratio of D to G bands gradually increased, while that of 2D to G bands decreased, due to increasing imidazole concentration. The yield of CN x made from mixtures of imidazole and acetonitrile can reach 192 mg in 24 min, which is 15 times that of CN x prepared from only acetonitrile. The aligned CN x, with controlled nitrogen doping, tunable structure and high yield, may find applications in developing non-noble catalysts and novel catalyst supports for fuel cells.

  15. Nitrogen-doped carbon nanotubes with tunable structure and high yield produced by ultrasonic spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Liu Jian; Zhang Yong; Ionescu, Mihnea Ioan; Li Ruying [Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON, N6A 5B9 (Canada); Sun Xueliang, E-mail: xsun@eng.uwo.ca [Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON, N6A 5B9 (Canada)

    2011-06-15

    Nitrogen-doped carbon nanotubes (CN{sub x}) were prepared by ultrasonic spray pyrolysis from mixtures of imidazole and acetonitrile. Imidazole, as an additive, was used to control the structure and nitrogen doping in CN{sub x} by adjusting its concentration in the mixtures. Scanning electron microscopy observation showed that the addition of imidazole increased the nanotube growth rate and yield, while decreased the nanotube diameter. Transmission electron microscopy study indicated that the addition of imidazole promoted the formation of a dense bamboo-like structure in CN{sub x}. X-ray photoelectron spectroscopy analysis demonstrated that the nitrogen content varied from 3.2 to 5.2 at.% in CN{sub x} obtained with different imidazole concentrations. Raman spectra study showed that the intensity ratio of D to G bands gradually increased, while that of 2D to G bands decreased, due to increasing imidazole concentration. The yield of CN{sub x} made from mixtures of imidazole and acetonitrile can reach 192 mg in 24 min, which is 15 times that of CN{sub x} prepared from only acetonitrile. The aligned CN{sub x}, with controlled nitrogen doping, tunable structure and high yield, may find applications in developing non-noble catalysts and novel catalyst supports for fuel cells.

  16. Synthesis of Nitrogen-Doped Carbon Nanocoils with Adjustable Morphology using Ni–Fe Layered Double Hydroxides as Catalyst Precursors

    Directory of Open Access Journals (Sweden)

    Tomohiro Iwasaki

    2015-01-01

    Full Text Available Nitrogen-doped carbon nanocoils (CNCs with adjusted morphologies were synthesized in a one-step catalytic chemical vapour deposition (CVD process using acetoni‐ trile as the carbon and nitrogen source. The nickel iron oxide/nickel oxide nanocomposites, which were derived from nickel–iron layered double hydroxide (LDH precur‐ sors, were employed as catalysts for the synthesis of CNCs. In this method, precursor-to-catalyst transformation, catalyst activation, formation of CNCs, and nitrogen doping were all performed in situ in a single process. The morphology (coil diameter, coil pitch, and fibre diameter and nitrogen content of the synthesized CNCs was indi‐ vidually adjusted by modulation of the catalyst composi‐ tion and CVD reaction temperature, respectively. The adjustable ranges of the coil diameter, coil pitch, fibre diameter, and nitrogen content were confirmed to be approximately 500±100 nm, 600±100 nm, 100±20 nm, and 1.1±0.3 atom%, respectively.

  17. Microbiotic crusts on soil, rock and plants: neglected major players in the global cycles of carbon and nitrogen?

    Science.gov (United States)

    Elbert, W.; Weber, B.; Büdel, B.; Andreae, M. O.; Pöschl, U.

    2009-07-01

    Microbiotic crusts consisting of bacteria, fungi, algae, lichens, and bryophytes colonize most terrestrial surfaces, and they are able to fix carbon and nitrogen from the atmosphere. Here we show that microbiotic crusts are likely to play major roles in the global biogeochemical cycles of carbon and nitrogen, and we suggest that they should be further characterized and taken into account in studies and models of the Earth system and climate. For the global annual net uptake of carbon by microbiotic crusts we present a first estimate of ~3.6 Pg a-1. This uptake corresponds to ~6% of the estimated global net carbon uptake by terrestrial vegetation (net primary production, NPP: ~60 Pg a-1), and it is of the same magnitude as the global annual carbon turnover due to biomass burning. The estimated rate of nitrogen fixation by microbiotic crusts (~45 Tg a-1) amounts to ~40% of the global estimate of biological nitrogen fixation (107 Tg a-1). With regard to Earth system dynamics and global change, the large contribution of microbiotic crusts to nitrogen fixation is likely to be important also for the sequestration of CO2 by terrestrial plants (CO2 fertilization), because the latter is constrained by the availability of fixed nitrogen.

  18. Microbiotic crusts on soil, rock and plants: neglected major players in the global cycles of carbon and nitrogen?

    Directory of Open Access Journals (Sweden)

    W. Elbert

    2009-07-01

    Full Text Available Microbiotic crusts consisting of bacteria, fungi, algae, lichens, and bryophytes colonize most terrestrial surfaces, and they are able to fix carbon and nitrogen from the atmosphere. Here we show that microbiotic crusts are likely to play major roles in the global biogeochemical cycles of carbon and nitrogen, and we suggest that they should be further characterized and taken into account in studies and models of the Earth system and climate.

    For the global annual net uptake of carbon by microbiotic crusts we present a first estimate of ~3.6 Pg a−1. This uptake corresponds to ~6% of the estimated global net carbon uptake by terrestrial vegetation (net primary production, NPP: ~60 Pg a−1, and it is of the same magnitude as the global annual carbon turnover due to biomass burning. The estimated rate of nitrogen fixation by microbiotic crusts (~45 Tg a−1 amounts to ~40% of the global estimate of biological nitrogen fixation (107 Tg a−1. With regard to Earth system dynamics and global change, the large contribution of microbiotic crusts to nitrogen fixation is likely to be important also for the sequestration of CO2 by terrestrial plants (CO2 fertilization, because the latter is constrained by the availability of fixed nitrogen.

  19. Exogenous nutrients and carbon resource change the responses of soil organic matter decomposition and nitrogen immobilization to nitrogen deposition.

    Science.gov (United States)

    He, Ping; Wan, Song-Ze; Fang, Xiang-Min; Wang, Fang-Chao; Chen, Fu-Sheng

    2016-03-29

    It is unclear whether exogenous nutrients and carbon (C) additions alter substrate immobilization to deposited nitrogen (N) during decomposition. In this study, we used laboratory microcosm experiments and (15)N isotope tracer techniques with five different treatments including N addition, N+non-N nutrients addition, N+C addition, N+non-N nutrients+C addition and control, to investigate the coupling effects of non-N nutrients, C addition and N deposition on forest floor decomposition in subtropical China. The results indicated that N deposition inhibited soil organic matter and litter decomposition by 66% and 38%, respectively. Soil immobilized (15)N following N addition was lowest among treatments. Litter (15)N immobilized following N addition was significantly higher and lower than that of combined treatments during the early and late decomposition stage, respectively. Both soil and litter extractable mineral N were lower in combined treatments than in N addition treatment. Since soil N immobilization and litter N release were respectively enhanced and inhibited with elevated non-N nutrient and C resources, it can be speculated that the N leaching due to N deposition decreases with increasing nutrient and C resources. This study should advance our understanding of how forests responds the elevated N deposition.

  20. Unusually high dispersion of nitrogen-doped carbon nanotubes in DNA solution.

    Science.gov (United States)

    Kim, Jin Hee; Kataoka, Masakazu; Fujisawa, Kazunori; Tojo, Tomohiro; Muramatsu, Hiroyuki; Vega-Díaz, Sofía M; Tristán-López, F; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Terrones, Mauricio; Dresselhaus, Mildred S

    2011-12-08

    The dispersibility in a DNA solution of bundled multiwalled carbon nanotubes (MWCNTs), having different chemical functional groups on the CNT sidewall, was investigated by optical spectroscopy. We observed that the dispersibility of nitrogen (N)-doped MWCNTs was significantly higher than that of pure MWCNTs and MWCNTs synthesized in the presence of ethanol. This result is supported by the larger amount of adsorbed DNA on N-doped MWCNTs, as well as by the higher binding energy established between nucleobases and the N-doped CNTs. Pure MWCNTs are dispersed in DNA solution via van der Waals and hydrophobic interactions; in contrast, the nitrogenated sites within N-doped MWCNTs provided additional sites for interactions that are important to disperse nanotubes in DNA solutions.

  1. Efficient and durable hydrogen evolution electrocatalyst based on nonmetallic nitrogen doped hexagonal carbon

    Science.gov (United States)

    Liu, Yanming; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

    2014-10-01

    The feasibility of renewable energy technology, hydrogen production by water electrolysis, depends on the design of efficient and durable electrocatalyst composed of earth-abundant elements. Herein, a highly active and stable nonmetallic electrocatalyst, nitrogen doped hexagonal carbon (NHC), was developed for hydrogen production. It exhibited high activity for hydrogen evolution with a low overpotential of only 65 mV, an apparent exchange current density of 5.7 × 10-2 mA cm-2 and a high hydrogen production rate of 20.8 mL cm-2 h-1 at -0.35 V. The superior hydrogen evolution activity of NHC stemmed from the intrinsic electrocatalytic property of hexagonal nanodiamond, the rapid charge transfer and abundance of electrocatalytic sites after nitrogen doping. Moreover, NHC was stable in a corrosive acidic solution during electrolysis under high current density.

  2. Effect of sulfur on enhancing nitrogen-doping and magnetic properties of carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Wang Kunlin

    2011-01-01

    Full Text Available Abstract Sulfur (S is introduced as an additive in the growth atmosphere of carbon nanotubes (CNTs in the range of 940-1020°C. CNT products with distorted sidewalls can be obtained by S-assisted growth. Moreover, many fascinating CNT structures can also be found in samples grown with S addition, such as bamboo-like CNTs, twisted CNTs, arborization-like CNTs, and bead-like CNTs. Compared with CNTs grown without S, more nitrogen-doping content is achieved in CNTs with S addition, which is beneficial for the properties and applications of nitrogen-doped CNTs. In addition, S can also enhance the encapsulation of ferromagnetic materials and thus improve the soft magnetic properties of CNTs, which is favorable to the applications of CNTs in the electromagnetic wave-absorbing and magnetic data storage areas.

  3. Amount, composition and seasonality of dissolved organic carbon and nitrogen export from agriculture in contrasting climates

    DEFF Research Database (Denmark)

    Graeber, Daniel; Meerhof, Mariana; Zwirnmann, Elke

    2014-01-01

    Agricultural catchments are potentially important but often neglected sources of dissolved organic matter (DOM), of which a large part is dissolved organic carbon (DOC) and nitrogen (DON). DOC is an important source of aquatic microbial respiration and DON may be an important source of nitrogen...... to aquatic ecosystems. However, there is still a lack of comprehensive studies on the amount, composition and seasonality of DOM export from agricultural catchments in different climates. The aim of our study was to assess the amount, composition and seasonality of DOM in a total of four streams in the wet......-temperate and subtropical climate of Denmark and Uruguay, respectively. In each climate, we investigated one stream with extensive agriculture (mostly pasture) and one stream with intensive agriculture (mostly intensively used arable land) in the catchment. We sampled each stream taking grab samples fortnightly for two...

  4. Amount, composition and seasonality of dissolved organic carbon and nitrogen export from agriculture in contrasting climates

    DEFF Research Database (Denmark)

    Graeber, Daniel; Goyenola, Guillermo; Meerhoff, Marianna

    Agricultural catchments are potentially important but often neglected sources of dissolved organic matter (DOM), of which a large part is dissolved organic carbon (DOC) and nitrogen (DON). DOC is an important source of aquatic microbial respiration and DON may be an important source of nitrogen...... to aquatic ecosystems. However, there is still a lack of comprehensive studies on the amount, composition and seasonality of DOM export from agricultural catchments in different climates. The aim of our study was to assess the amount, composition and seasonality of DOM in a total of four streams in the wet......-temperate and subtropical climate of Denmark and Uruguay, respectively. In each climate, we investigated one stream with extensive agriculture (mostly pasture) and one stream with intensive agriculture (mostly intensively used arable land) in the catchment. We sampled each stream taking grab samples fortnightly for two...

  5. Effect of sulfur on enhancing nitrogen-doping and magnetic properties of carbon nanotubes

    Science.gov (United States)

    Cui, Tongxiang; Lv, Ruitao; Huang, Zheng-Hong; Kang, Feiyu; Wang, Kunlin; Wu, Dehai

    2011-12-01

    Sulfur (S) is introduced as an additive in the growth atmosphere of carbon nanotubes (CNTs) in the range of 940-1020°C. CNT products with distorted sidewalls can be obtained by S-assisted growth. Moreover, many fascinating CNT structures can also be found in samples grown with S addition, such as bamboo-like CNTs, twisted CNTs, arborization-like CNTs, and bead-like CNTs. Compared with CNTs grown without S, more nitrogen-doping content is achieved in CNTs with S addition, which is beneficial for the properties and applications of nitrogen-doped CNTs. In addition, S can also enhance the encapsulation of ferromagnetic materials and thus improve the soft magnetic properties of CNTs, which is favorable to the applications of CNTs in the electromagnetic wave-absorbing and magnetic data storage areas.

  6. Structural and Electrical Properties of Amorphous Hydrogen Carbon-Nitrogen Films

    Institute of Scientific and Technical Information of China (English)

    SUO Da-Cheng; LIU Yi-Chun; LIU Yan; QI Xiu-Ying; ZHONG Dian-Qiang

    2004-01-01

    @@ Amorphous hydrogenated carbon-nitrogen (a-C:H:(N)) films with different nitrogen contents have been deposited by using rf-sputtering of a high purity graphite target in an Ar-H2-N2 atmosphere. Transmittance and reflectance spectra are used to characterize the Tauc gap and absorption coefficients in the wavelength range 0.185-3.2μm.The temperature dependence of conductivity demonstrates a hopping mechanism of the Fermi level in the temperature range of 77-300K. The density of state at the Fermi level is derived from the direct current conductivity.The photoluminescence properties of a-C:H:N films were investigated. The photoluminescence peak has a blue shift with increasing excitation energy. These results are discussed on the basis of a model in which the different sp2 clusters dispersed in sp3 matrices.

  7. Tailoring Pore Size of Nitrogen-Doped Hollow Carbon Nanospheres for Confi ning Sulfur in Lithium–Sulfur Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Weidong [General Motors Global Research and Development Center, Warren, MI (United States); Wang, Chong M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhang, Quiglin [General Motors Global Research and Development Center, Warren, MI (United States); Abruna, Hector D. [Cornell Univ., Ithaca, NY (United States); He, Yang [Univ. of Pittsburgh, PA (United States); Wang, Jiangwei [Univ. of Pittsburgh, PA (United States); Mao, Scott X. [Univ. of Pittsburgh, PA (United States); Xiao, Xingcheng [General Motors Global Research and Development Center, Warren, MI (United States)

    2015-08-19

    Three types of nitrogen-doped hollow carbon spheres with different pore sized porous shells are prepared to investigate the performance of sulfur confinement. The reason that why no sulfur is observed in previous research is determined and it is successfully demonstrated that the sulfur/polysulfide will overflow the porous carbon during the lithiation process.

  8. Effects of cryptogamic covers on the global carbon and nitrogen balance as investigated by different approaches

    Science.gov (United States)

    Weber, Bettina; Porada, Philipp; Elbert, Wolfgang; Burrows, Susannah; Caesar, Jennifer; Steinkamp, Jörg; Tamm, Alexandra; Andreae, Meinrat O.; Büdel, Burkhard; Kleidon, Axel; Pöschl, Ulrich

    2014-05-01

    Cryptogamic covers are composed of cyanobacteria, green algae, lichens, bryophytes, fungi and bacteria in varying proportions. As cryptogamic ground covers, comprising biological soil and rock crusts they occur on many terrestrial ground surfaces. Cryptogamic plant covers, containing epiphytic and epiphyllic crusts as well as foliose or fruticose lichens and bryophytes spread over large portions of terrestrial plant surfaces. Photoautotrophic organisms within these crusts sequester atmospheric CO2 and many of them include nitrogen-fixing cyanobacteria, utilizing atmospheric N2 to form ammonium which can be readily used by vascular plants. In a large-scale data analysis approach, we compiled all available data on the physiological properties of cryptogamic covers and developed a model to calculate their annual nitrogen fixation and net primary production. Here, we obtained a total value of 3.9 Pg a-1 for the global net uptake of carbon by cryptogamic covers, which corresponds to approximately 7% of the estimated global net primary production of terrestrial vegetation. Nitrogen assimilation of cryptogamic covers revealed a global estimate of ~49 Tg a-1, accounting for as much as about half the estimated total terrestrial biological nitrogen fixation. In a second approach, we calculated the global carbon uptake by lichens and bryophytes by means of a process-based model. In this model, we used gridded climate data combined with key habitat properties (as e.g. disturbance intervals) to predict the processes which control net carbon uptake, i.e. photosynthesis, respiration, water uptake and evaporation. The model relies on equations frequently used in dynamic vegetation models, which were combined with concepts specific to lichens and bryophytes. As this model only comprises lichens and bryophytes, the predicted terrestrial net uptake of 0.34 to 3.3 Gt a-1 is in accordance with our empirically-derived estimate. Based on this result, we quantified the amount of nitrogen

  9. Electrical and Electrochemical Properties of Nitrogen-Containing Tetrahedral Amorphous Carbon (ta-C) Thin Films

    Science.gov (United States)

    Yang, Xingyi

    Tetrahedral amorphous carbon (ta-C) is a diamond-like carbon (DLC) material comprised of a mixture of sp2 (˜40%) and sp3-bonded (˜60%) carbon domains. The physicochemical structure and electrochemical properties depend strongly on the sp2/sp3 bonding ratio as well as the incorporation of impurities, such as hydrogen or nitrogen. The ability to grow ta-C films at lower temperatures (25-100 °C) on a wider variety of substrates is a potential advantage of these materials as compared with diamond films. In this project, the basic structural and electrochemical properties of nitrogen-incorporated ta-C thin films will be discussed. The major goal of this work was to determine if the ta-C:N films exhibit electrochemical properties more closely aligned with those of boron-doped diamond (sp 3 carbon) or glassy carbon (amorphous sp2 carbon). Much like diamond, ta-C:N thin-film electrodes are characterized by a low background voltammetric current, a wide working potential window, relatively rapid electron-transfer kinetics for aqueous redox systems, such as Fe(CN) 6-3/-4 and Ru(NH3)6+3/+2 , and weak adsorption of polar molecules from solution. For example, negligible adsorption of methylene blue was found on the ta-C:N films in contrast to glassy carbon; a surface on which this molecule strongly adsorbs. The film microstructure was studied with x-ray photoelectron microscopy (XPS), visible Raman spectroscopy and electron-energy loss spectroscopy (EELS); all of which revealed the sp2-bonded carbon content increased with increasing nitrogen. The electrical properties of ta-C:N films were studied by four-point probe resistance measurement and conductive-probe AFM (CP-AFM). The incorporation of nitrogen into ta-C films increased the electrical conductivity primarily by increasing the sp2-bonded carbon content. CP-AFM showed the distribution of the conductive sp2-carbon on the film surface was not uniform. These films have potential to be used in field emission area. The

  10. Soil carbon and nitrogen dynamics in the first year following herbicide and scalping in a revegetation trial in south-east Queensland, Australia.

    Science.gov (United States)

    Hosseini Bai, Shahla; Xu, Zhihong; Blumfield, Timothy J; Wild, Clyde H; Chen, Chengrong

    2014-04-01

    During revegetation, the maintenance of soil carbon (C) pools and nitrogen (N) availability is considered essential for soil fertility and this study aimed to evaluate contrasting methods of site preparation (herbicide and scalping) with respect to the effects on soil organic matter (SOM) during the critical early establishment phase. Soil total C (TC), total N (TN), hot-water extractable organic C (HWEOC), hot-water extractable total N (HWETN), microbial biomass C and N (MBC and MBN), total inorganic N (TIN) and potentially mineralizable N (PMN) were measured over 53 weeks. MBC and MBN were the only variables affected by herbicide application. Scalping caused an immediate reduction in all variables, and the values remained low without any sign of recovery for the period of the study. The impact of scalping on HWETN and TIN lasted 22 weeks and stabilised afterwards. MBC and MBN were affected by both herbicide and scalping after initial treatment application and remained lower than control during the period of the study but did not decrease over time. While scalping had an inevitable impact on all soil properties that were measured, that impact did not worsen over time, and actually improved plant growth (unpublished data) while reducing site establishment costs. Therefore, it provides a useful alternative for weed control in revegetation projects where it is applied only once at site establishment and where SOM would be expected to recover as canopy closure is obtained and nutrient cycling through litterfall commences.

  11. [Characteristics of 'salt island' and 'fertile island' for Tamarix chinensis and soil carbon, nitrogen and phosphorus ecological stoichiometry in saline-alkali land].

    Science.gov (United States)

    Zhang, Li-hua; Chen, Xiao-bing

    2015-03-01

    To clarify the nutrient characteristics of 'salt island' and 'fertile island' effects in saline-alkali soil, the native Tamarix chinensis of the Yellow River Delta (YRD) was selected to measure its soil pH, electrical conductivity (EC), organic carbon (SOC), total nitrogen (N), total phosphorus (P) and their stoichiometry characteristics at different soil depths. The results showed that soil pH and EC increased with the increasing soil depth. Soil EC and P in the 0-20 cm layer decreased and increased from canopied area to interspace, respectively. SOC, N, N/P and C/P in the 20-40 cm soil layer decreased, and C/N increased from the shrub center to interspace. SOC and N contents between island and interspace both decreased but P content decreased firstly and then increased with the increasing soil depth. Soil pH correlated positively with EC. In addition, pH and EC correlated negatively with C, N, P contents and their ecological stoichiometry.

  12. Effect of carbon and nitrogen sources on carotenoids production by native strain of Aurantiochytrium Ch25

    Directory of Open Access Journals (Sweden)

    Mahdiye Esmizade

    2016-09-01

    Full Text Available Introduction: Microorganisms produce carotenoids as a part of their response to environmental stresses. Carotenoids have many applications in human health, such as antioxidant, anti-cancer, light protection activity and as a precursor for hormones. Materials and methods: In this study, the effect of different carbon and nitrogen sources was evaluated on carotenoids production by native Aurantiochytrium strain. The effects of different carbon and nitrogen sources were studied on biomass and carotenoid production. Then, carotenoids were extracted and analyzed by TLC, spectrophotometry and HPLC methods. Results: Results showed that glycerol is the best carbon source for production of high carotenoids content. Selected medium contained: glycerol (1.5% v/v, peptone (1g/l, yeast extract (1g/l and 50% of sea water. Total carotenoids content was 134.8 µg/g CDW in this medium. TLC analysis showed that the extracted carotenoid is included: beta-carotene, astaxanthin monoester, astaxanthin diester and free astaxanthin. The results of HPLC analysis showed presence of astaxanthin, canthaxanthin, echinenone and β-carotene in the carotenoid extract. Discussion and conclusion: In this research, production of carotenoids was investigated in native strain of Aurantiochytrium and carotenoids profile was included astaxanthin, canthaxanthin, β-carotene and echinenone.

  13. Trophic ecology of small yellow croaker (Larimichthys polyactis Bleeker): stable carbon and nitrogen isotope evidence

    Institute of Scientific and Technical Information of China (English)

    JI Weiwei; CHEN Xuezhong; JIANG Yazhou; LI Shengfa

    2011-01-01

    The trophic ecology of the small yellow croaker (Larimichthys polyactis) was studied using stable isotope analyses.Samples were collected from July to September 2009 and 34 individuals from eight sites were examined for stable carbon and nitrogen isotopes.Stable carbon isotope ratios (δ13C)ranged from -20.67 to -15.43,while stable nitrogen isotope ratios (δ15N) ranged 9.18-12.23.The relationship between δ13C and δ15N suggested high resource partitioning in the sampling area.Significant differences in stable isotope values among the eight sampling sites may be linked to environmental diversities involving various physical processes (such as ocean current,wind and tide) and different carbon sources.Furthermore,the stable isotope ratios may also explain the ontogenetic variability in diet and feeding,because δ13C and δ15N varied significantly with increasing body size.The findings are consistent with other studies on diet analyses in small yellow croaker.It was also demonstrated that stable isotope analysis could be used to estimate the trophic characters of small yellow croaker in feeding patterns and migrating habits.

  14. Secondary brown carbon formation via the dicarbonyl imine pathway: nitrogen heterocycle formation and synergistic effects.

    Science.gov (United States)

    Kampf, C J; Filippi, A; Zuth, C; Hoffmann, T; Opatz, T

    2016-07-21

    Dicarbonyls are known to be important precursors of so-called atmospheric brown carbon, significantly affecting aerosol optical properties and radiative forcing. In this systematic study we report the formation of light-absorbing nitrogen containing compounds from simple 1,2-, 1,3-, 1,4-, and 1,5-dicarbonyl + amine reactions. A combination of spectrophotometric and mass spectrometric techniques was used to characterize reaction products in solutions mimicking atmospheric particulates. Experiments with individual dicarbonyls and dicarbonyl mixtures in ammonium sulfate and glycine solutions demonstrate that nitrogen heterocycles are common structural motifs of brown carbon chromophores formed in such reaction systems. 1,4- and 1,5-dicarbonyl reaction systems, which were used as surrogates for terpene ozonolysis products, showed rapid formation of light-absorbing material and products with absorbance maxima at ∼450 nm. Synergistic effects on absorbance properties were observed in mixed (di-)carbonyl experiments, as indicated by the formation of a strong absorber in ammonium sulfate solutions containing acetaldehyde and acetylacetone. This cross-reaction oligomer shows an absorbance maximum at 385 nm, relevant for the actinic flux region of the atmosphere. This study demonstrates the complexity of secondary brown carbon formation via the imine pathway and highlights that cross-reactions with synergistic effects have to be considered an important pathway for atmospheric BrC formation.

  15. Development of nitrogen enriched nanostructured carbon adsorbents for CO2 capture.

    Science.gov (United States)

    Goel, Chitrakshi; Bhunia, Haripada; Bajpai, Pramod K

    2015-10-01

    Nanostructured carbon adsorbents containing high nitrogen content were developed by templating melamine-formaldehyde resin in the pores of mesoporous silica by nanocasting technique. A series of adsorbents were prepared by altering the carbonization temperature from 400 to 700 °C and characterized in terms of their textural and morphological properties. CO2 adsorption performance was investigated at various temperatures from 30 to 100 °C by using a thermogravimetric analyzer under varying CO2 concentrations. Multiple adsorption-desorption experiments were also carried out to investigate the adsorbent regenerability. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the development of nanostructured materials. Fourier transform infrared spectroscopy (FTIR) and elemental analysis indicated the development of carbon adsorbents having high nitrogen content. The surface area and pore volume of the adsorbent carbonized at 700 °C were found to be 266 m(2) g(-1) and 0.25 cm(3) g(-1) respectively. CO2 uptake profile for the developed adsorbents showed that the maximum CO2 adsorption occurred within ca. 100 s. CO2 uptake of 0.792 mmol g(-1) at 30 °C was exhibited by carbon obtained at 700 °C with complete regenerability in three adsorption-desorption cycles. Furthermore, kinetics of CO2 adsorption on the developed adsorbents was studied by fitting the experimental data of CO2 uptake to three kinetic models with best fit being obtained by fractional order kinetic model with error% within range of 5%. Adsorbent surface was found to be energetically heterogeneous as suggested by Temkin isotherm model. Also the isosteric heat of adsorption for CO2 was observed to increase from ca. 30-44 kJ mol(-1) with increase in surface coverage.

  16. Non-Redfield carbon and nitrogen cycling in the Arctic: Effects of ecosystem structure and dynamics

    Science.gov (United States)

    Daly, Kendra L.; Wallace, Douglas W. R.; Smith, Walker O.; Skoog, Annelie; Lara, RubéN.; Gosselin, Michel; Falck, Eva; Yager, Patricia L.

    1999-02-01

    The C:N ratio is a critical parameter used in both global ocean carbon models and field studies to understand carbon and nutrient cycling as well as to estimate exported carbon from the euphotic zone. The so-called Redfield ratio (C:N = 6.6 by atoms) [Redfield et al., 1963] is widely used for such calculations. Here we present data from the NE Greenland continental shelf that show that most of the C:N ratios for particulate (autotrophic and heterotrophic) and dissolved pools and rates of transformation among them exceed Redfield proportions from June to August, owing to species composition, size, and biological interactions. The ecosystem components that likely comprised sinking particles and had relatively high C:N ratios (geometric means) included (1) the particulate organic matter (C:N = 8.9) dominated by nutrient-deficient diatoms, resulting from low initial nitrate concentrations (approximately 4 μM) in Arctic surface waters; (2) the dominant zooplankton, herbivorous copepods (C:N = 9.6), having lipid storage typical of Arctic copepods; and (3) copepod fecal pellets (C:N = 33.2). Relatively high dissolved organic carbon concentrations (median 105 μM) were approximately 25 to 45 μM higher than reported for other systems and may be broadly characteristic of Arctic waters. A carbon-rich dissolved organic carbon pool also was generated during summer. Since the magnitude of carbon and nitrogen uncoupling in the surface mixed layer appeared to be greater than in other regions and occurred throughout the productive season, the C:N ratio of particulate organic matter may be a better conversion factor than the Redfield ratio to estimate carbon export for broad application in northern high-latitude systems.

  17. [Storage and allocation of carbon and nitrogen in Robinia pseudoacacia plantation at different ages in the loess hilly region, China].

    Science.gov (United States)

    Ai, Ze-Min; Chen, Yun-Ming; Cao, Yang

    2014-02-01

    The 9-, 17-, 30- and 37-year-old Robinia pseudoacacia plantations in the loess hilly region were investigated to study the dynamics and allocation patterns of carbon and nitrogen storage. The results showed that the ranges of carbon and nitrogen contents were 435.9-493.4 g x kg(-1) and 6.8-21.0 g x kg(-1) in the arbor layer, 396.3-459.2 g x kg(-1) and 14.2-23.5 g x kg(-1) in the herb and litter layer, and 2.7-10.7 g x kg(-1) and 0.2-0.7 g x kg(-1) in the soil layer, respectively. The branch was the major carbon and nitrogen pool in the arbor layer, accounting for 46.9%-63.3% and 39.3%-57.8%, respectively. The maximum storage values were 30.1 and 1.8 Mg x hm(-2) for carbon and nitrogen, respectively, in the 0-20 cm soil layer in the 37-year-old R. pseudoacacia plantation. The total carbon and nitrogen storage in the R. pseudoacacia plantation ecosystem increased with increasing forest age, and the maximum values were 127.9 Mg x hm(-2) and 6512.8 kg x hm(-2) for carbon and nitrogen storage, respectively, in the 37-year-old R. pseudoacacia plantation. Soil layer was the major carbon and nitrogen pool of R. pseudoacacia plantation ecosystem, accounting for 63.3%-83.3% and 80.3%-91.4%, respectively.

  18. Long-term Carbon and Nitrogen Dynamics at SPRUCE Revealed through Stable Isotopes in Peat Profiles

    Science.gov (United States)

    Hobbie, E. A.

    2015-12-01

    Carbon and nitrogen turnover in peatlands is of considerable interest because peat is a large reservoir of stored carbon that could emit greenhouse gases in response to climate change. Because peat cores preserve a long-term record of system carbon and nitrogen dynamics, it is possible to use stable isotopes as markers of changes in carbon (C) and nitrogen (N) dynamics over time. Here, we used δ15N and δ13C patterns throughout the depth profile of peat cores to understand controls over C-N cycling in the Marcell S1 forested bog in northern Minnesota. In multiple regression analyses, δ15N and δ13C correlated strongly with depth, plot location, %C, %N, and each other. Negative correlation of δ15N with %N presumably reflected removal of 15N-depleted N via denitrification, diffusion, or plant N transfer via mycorrhizal fungi. A step increase in the depth coefficient for δ15N of ~3‰ from -25 cm to -35 cm suggested that the N removal process primarily operates at a discrete depth corresponding to the juncture between aerobic and anaerobic layers defined by the water table. Higher δ15N and lower δ13C in plots closer to uplands may reflect distinct hydrology and accompanying shifts in C and N dynamics in the lagg area fringing the bog. The Suess effect (declining δ13CO2 since the Industrial Revoluation) and aerobic decomposition lowered δ13C in recent surficial samples. Small increases in δ13C at -112 cm (4300 calibrated years BP) and -85 cm (3800 calibrated years BP) may reflect C dynamics during a suspected transitional fen stage (based on paleoecology at a nearby bog), when reduced methanotrophy retained less 13C-depleted carbon derived from methane than in later periods. The C/N decreased until about -85 cm and thereafter remained steady, suggesting that the active zone of aerobic processing during drought may extend to this depth. The inflection point in calculated carbon accumulation rates at this depth supports this conclusion.

  19. Metal-Organic Framework Derived Hierarchically Porous Nitrogen-Doped Carbon Nanostructures as Novel Electrocatalyst for Oxygen Reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Shaofang; Zhu, Chengzhou; Zhou, Yazhou; Yang, Guohai; Jeon, Ju Won; Lemmon, John P.; Du, Dan; Nune, Satish K.; Lin, Yuehe

    2015-10-01

    The hierarchically porous nitrogen-doped carbon materials, derived from nitrogen-containing isoreticular metal-organic framework-3 (IRMOF-3) through direct carbonization, exhibited excellent electrocatalytic activity in alkaline solution for oxygen reduction reaction (ORR). This high activity is attributed to the 10 presence of high percentage of quaternary and pyridinic nitrogen, the high surface area as well as good conductivity. When IRMOF-3 was carbonized at 950 °C (CIRMOF-3-950), it showed four-electron reduction pathway for ORR and exhibited better stability (about 78.5% current density was maintained) than platinum/carbon (Pt/C) in the current durability test. In addition, CIRMOF-3-950 presented high selectivity to cathode reactions compared to commercial Pt/C.

  20. Variability in carbon and nitrogen isotope fractionation associated with bacterial hydrolysis of atrazine

    Science.gov (United States)

    Meyer, A.; Penning, H.; Elsner, M.

    2009-04-01

    Even after legislative prohibition in 1991 by the European Union, the pesticide atrazine and its metabolites are still detected in surface and ground water frequently exceeding the permitted drinking water concentration limit of 0,1 g/L. Despite much recent research on atrazine, its risk assessment in the environment is still a major challenge because of the difficulty of establishing mass balances in the subsurface. To obtain a better insight into the fate of atrazine, we developed compound-specific stable isotope analysis (CSIA) for atrazine. CSIA has proven valuable for assessing organic contaminants in subsurface environments, on the one hand for source identification and on the other hand to trace (bio)chemical degradation reactions through isotope fractionation in the compounds. Such assessment is based on the Rayleigh equation and therein on the isotope enrichment factor ɛ, which must be determined experimentally beforehand. In ongoing work, we therefore measured carbon and nitrogen isotope fractionation associated with biotic hydrolsis of atrazine. C and N isotope enrichment factors were determined in resting cell experiments for Pseudomonas sp. ADP, Chelatobacter heintzii and Arthrobacter aurescens TC1, strains that hydrolyse atrazine in the initial transformation reaction. Carbon and nitrogen isotope enrichment factors were distinctly different between the bacterial strains. However, when plotting shifts in carbon isotope ratios versus shifts in nitrogen isotope ratios the slopes of the different degradation experiments coincided well. These results give evidence that all bacterial strains were carrying out the same initial biochemical degradation reaction, but that the associated isotope fractionation, as represented by the enrichment factors, was masked to a different extent owing to different rate determining steps prior to the isotopically sensitive bond cleavage (commitment to catalysis). Our study therefore illustrates the benefit of multi

  1. State factor relationships of dissolved organic carbon and nitrogen losses from unpolluted temperate forest watersheds

    Science.gov (United States)

    Perakis, S.S.; Hedin, L.O.

    2007-01-01

    We sampled 100 unpolluted, old-growth forested watersheds, divided among 13 separate study areas over 5 years in temperate southern Chile and Argentina, to evaluate relationships among dominant soil-forming state factors and dissolved carbon and nitrogen concentrations in watershed streams. These watersheds provide a unique opportunity to examine broad-scale controls over carbon (C) and nitrogen (N) biogeochemistry in the absence of significant human disturbance from chronic N deposition and land use change. Variations in the ratio dissolved organic carbon (DOC) to nitrogen (DON) in watershed streams differed by underlying soil parent material, with average C:N = 29 for watersheds underlain by volcanic ash and basalt versus C:N = 73 for sedimentary and metamorphic parent materials, consistent with stronger adsorption of low C:N hydrophobic materials by amorphous clays commonly associated with volcanic ash and basalt weathering. Mean annual precipitation was related positively to variations in both DOC (range: 0.2-9.7 mg C/L) and DON (range: 0.008-0.135 mg N/L) across study areas, suggesting that variations in water volume and concentration may act synergistically to influence C and N losses across dry to wet gradients in these forest ecosystems. Dominance of vegetation by broadleaf versus coniferous trees had negligible effects on organic C and N concentrations in comparison to abiotic factors. We conclude that precipitation volume and soil parent material are important controls over chemical losses of dissolved organic C and N from unpolluted temperate forest watersheds. Our results raise the possibility that biotic imprints on watershed C and N losses may be less pronounced in naturally N-poor forests than in areas impacted by land use change and chronic N deposition. Copyright 2007 by the American Geophysical Union.

  2. Aspect of human food ecology; Development of carbon and nitrogen isotope method

    Energy Technology Data Exchange (ETDEWEB)

    Minagawa, Masao (Hokkaido Univ., Sapporo (Japan))

    1994-01-01

    The isotopic dietary analysis was applied for some prehistoric human populations from East Asia, Latin America, and Oceania region. Most samples were from archeological sites from 1000 to 6000 year's bp. Some modern ethnological groups including Tibet, Kurud, Shelpa and Tlingit were also studied for evaluating prehistoric human food habit. Carbon and nitrogen isotope compositions of gelatin fractions have been analyzed for prehistoric bone samples. Analytical procedure for isotopes and data analyses for reconstructing dietary composition was developed and tested by a modern human food system. A stochastic method based on the Monte Carlo model was applied to estimate dependency of major food resources having unique isotope compositions in carbon and nitrogen, and has showed consistent results to the statistic food consumption record in Japan. Carbon and nitrogen isotope composition of human tissues showed distinct difference among human groups in both prehistoric and modern samples. These data were evaluated by difference of dietary patterns: contributions of marine food, terrestrial food, meat, C3 and C4 plant, which are characterized by the difference of [sup 13]C and [sup 15]N content. On the basis of the stochastic feeding simulation, dietary consumption patterns were estimated for Jomon fisher-hunter-gatherers, historic Ainu, prehistoric east Siberian, prehistoric Latin American farmers in Mexico and Peru, and prehistoric fisheres in Cook island. Results showed a remarkable relationship between animal protein dependence and marine food usage. This result will be discussed from following two possibilities; the human adaptation on marine resources would be one of the important direction to upgrade animal protein uptake, or marine food could be used as alternative protein source for terrestrial game animals. (author).

  3. ORGANIC CARBON AND TOTAL NITROGEN IN THE DENSIMETRIC FRACTIONS OF ORGANIC MATTER UNDER DIFFERENT SOIL MANAGEMEN

    Directory of Open Access Journals (Sweden)

    MARCELO RIBEIRO VILELA PRADO

    2016-01-01

    Full Text Available The evaluation of land use and management by the measurement of soil organic matter and its fractions has gained attention since it helps in the understanding of the dynamics of their contribution to soil productivity, especially in tropical environments. This study was conducted in the municipality of Colorado do Oeste, state of Rondônia, Brazil and its aim was to determinethe quantity of organic carbon and total nitrogen in the light and heavy fractions of organic matter in the surface layers of a typic hapludalf under different land use systems: Native Forest: open evergreen forest, reference environment; Agroforestry System 1: teak (Tectona grandis LF and kudzu (Pueraria montana; Agroforestry System 2: coffee (Coffea canephora, marandu palisade grass (Brachiaria brizantha cv. Marandu, “pinho cuiabano” (Parkia multijuga, teak and kudzu.; Agroforestry System 3: teak and cocoa (Theobroma cacao; Silvopasture System: teak, cocoa and marandu palisade grass; and Extensive Grazing System: marandu palisade grass. The experimental design was a randomized block in split-split plots (use systems versus soil layers of 0-0.05 and 0.05-0.10 m with three replications. The results showed that relative to Native Forest, the Agroforestry System 2 had equal- and greater amounts of organic carbon and total nitrogen respectively (light and heavy fractions in the soil organic matter, with the light fraction being responsible for storage of approximately 45% and 70% of the organic carbon and total nitrogen, respectively. Therefore, the light densimetric fraction proved to be useful in the early identification of the general decline of the soil organic matter in the land use systems evaluated.

  4. Nitrogen deposition may enhance soil carbon storage via change of soil respiration dynamic during a spring freeze-thaw cycle period

    OpenAIRE

    Guoyong Yan; Yajuan Xing; Lijian Xu; Jianyu Wang; Wei Meng; Qinggui Wang; Jinghua Yu; Zhi Zhang; Zhidong Wang; Siling Jiang; Boqi Liu; Shijie Han

    2016-01-01

    As crucial terrestrial ecosystems, temperate forests play an important role in global soil carbon dioxide flux, and this process can be sensitive to atmospheric nitrogen deposition. It is often reported that the nitrogen addition induces a change in soil carbon dioxide emission in growing season. However, the important effects of interactions between nitrogen deposition and the freeze-thaw-cycle have never been investigated. Here we show nitrogen deposition delays spikes of soil respiration a...

  5. Medium term ecohydrological response of peatland bryophytes to canopy disturbance

    Science.gov (United States)

    Leonard, Rhoswen; Kettridge, Nick; Krause, Stefan; Devito, Kevin; Granath, Gustaf; Petrone, Richard; Mandoza, Carl; Waddington, James Micheal

    2016-04-01

    Canopy disturbance in northern forested peatlands is widespread. Canopy changes impact the ecohydrological function of moss and peat, which provide the principal carbon store within these carbon rich ecosystems. Different mosses have contrasting contributions to carbon and water fluxes (e.g. Sphagnum fuscum and Pleurozium schreberi) and are strongly influenced by canopy cover. As a result, changes in canopy cover lead to long-term shifts in species composition and associated ecohydrological function. Despite this, the medium-term response to such disturbance, the associated lag in this transition to a new ecohydrological and biogeochemical regime, is not understood. Here we investigate this medium term ecohydrological response to canopy removal using a randomised plot design within a north Albertan peatland. We show no significant ecohydrological change in treatment plots four years after canopy removal. Notably, Pleurozium schreberi and Sphagnum fuscum remained within respective plots post treatment and there was no significant difference in plot resistance to evapotranspiration or carbon exchange. Our results show that canopy removal alone has little impact on bryophyte ecohydrology in the short/medium term. This resistance to disturbance contrasts strongly with dramatic short-term changes observed within mineral soils suggesting that concurrent shifts in the large scale hydrology induced within such disturbances are necessary to cause rapid ecohydrological transitions. Understanding this lagged response is critical to determine the decadal response of carbon and water fluxes in response to disturbance and the rate at which important medium term ecohydrological feedbacks are invoked.

  6. Oxygen- and Nitrogen-Enriched 3D Porous Carbon for Supercapacitors of High Volumetric Capacity.

    Science.gov (United States)

    Li, Jia; Liu, Kang; Gao, Xiang; Yao, Bin; Huo, Kaifu; Cheng, Yongliang; Cheng, Xiaofeng; Chen, Dongchang; Wang, Bo; Sun, Wanmei; Ding, Dong; Liu, Meilin; Huang, Liang

    2015-11-11

    Efficient utilization and broader commercialization of alternative energies (e.g., solar, wind, and geothermal) hinges on the performance and cost of energy storage and conversion systems. For now and in the foreseeable future, the combination of rechargeable batteries and electrochemical capacitors remains the most promising option for many energy storage applications. Porous carbonaceous materials have been widely used as an electrode for batteries and supercapacitors. To date, however, the highest specific capacitance of an electrochemical double layer capacitor is only ∼200 F/g, although a wide variety of synthetic approaches have been explored in creating optimized porous structures. Here, we report our findings in the synthesis of porous carbon through a simple, one-step process: direct carbonization of kelp in an NH3 atmosphere at 700 °C. The resulting oxygen- and nitrogen-enriched carbon has a three-dimensional structure with specific surface area greater than 1000 m(2)/g. When evaluated as an electrode for electrochemical double layer capacitors, the porous carbon structure demonstrated excellent volumetric capacitance (>360 F/cm(3)) with excellent cycling stability. This simple approach to low-cost carbonaceous materials with unique architecture and functionality could be a promising alternative to fabrication of porous carbon structures for many practical applications, including batteries and fuel cells.

  7. NLCD 2001 - Tree Canopy

    Data.gov (United States)

    Minnesota Department of Natural Resources — The National Land Cover Database 2001 tree canopy layer for Minnesota (mapping zones 39-42, 50-51) was produced through a cooperative project conducted by the...

  8. [Response of black soil organic carbon, nitrogen and its availability to longterm fertilization].

    Science.gov (United States)

    Luo, Kun; Hu, Rong-Gui; Zhang, Wen-Ju; Zhou, Bao-Ku; Xu, Ming-Gang; Zhang, Jing-Ye; Xia, Ping-Ping

    2013-02-01

    Based on the long-term fertilization experiments, effects of various fertilization practices on the soil organic carbon (SOC) and total nitrogen (TN) in the surface (0-20 cm) and subsurface (20-40 cm) black soil in northeast China were studied. Results showed that, compared with the CK, long-term application of organic manure, especially the combination of mineral fertilizers and organic manure significantly increased the organic SOC and TN in the surface soil. Application of mineral fertilizers plus organic manure with conventional (NPM) and high application (N2P2M2) rate increased SOC significantly by 24. 6% and 25.1% , and TN by 29.5% and 32.8%, respectively. However, there was no significant difference among the treatments for SOC and TN at the subsurface. Compared with the CK (CKh), mineral fertilizer plus organic manure (NPM and N2P2M2) did not only increase the soil microbial biomass carbon (SMBC) and nitrogen (SMBN) , dissolved organic carbon (DOC) and nitrogen (DN), but also significantly increased the ratio of SMBC and DOC to SOC, SMBN and TN to TN. Application of the NPM and N2P2M2 increased the value of SMBC/SOC by 0.36 to 0.59 and SMBN/TN by 1.21 to 1.95 percentage points, respectively. The value of DOC/SOC and DN/TN ranged from 0.53% to 0.72% and 1.41% to 1.78%, respectively. This result indicated that SMBC, SMBN, DOC, DN and SMBC/ SOC, SMBN/TN, DOC/SOC, DN/TN were more sensitive than SOC and TN to long-term fertilization in the soil profile, and were better indicators for the impact of long-term fertilization soil fertility. The concluded that the application of manure especially manure plus mineral fertilizers can increase soil nutrients activity in the surface and subsurface black soil, acting as a helpful practice to improve soil fertility and the ability of nutrient supply, while it may cause potential environment pollution on carbon and nitrogen loss in the agroecosystem.

  9. Hydrogen adsorption of nitrogen-doped carbon nanotubes functionalized with 3d-block transition metals

    Indian Academy of Sciences (India)

    Michael R Mananghaya

    2015-04-01

    A systematic study of the most stable configurations, calculation of the corresponding binding and free energies of functionalized 3d transition metals (TMs) on (10,0) Single Walled Carbon Nanotube (SWCNT) doped with porphyrin-like nitrogen defects (4ND-CNxNT) using spin-polarized density functional theory (DFT) formalism with flavours of LDA and GGA exchange-correlation (XC) functionals has been made. A thorough analysis showed that the electronic and magnetic properties of SWCNT are dependent on the TMs absorbed wherein, the composite material TM/4ND-CNxNT can act as a medium for storing hydrogen at room temperature manifested through favourable adsorption energy.

  10. Soil carbon accumulation and nitrogen retention traits of four tree species grown in common gardens

    DEFF Research Database (Denmark)

    Gurmesa, Geshere Abdisa; Schmidt, Inger Kappel; Gundersen, Per

    2013-01-01

    Tree species effects on soil carbon (C) accumulation are uncertain, especially with respect to the mineral soil C, and the consistency of such effects across soil types is not known. The interaction between C accumulation and nitrogen (N) retention among common tree species has also been little...... differed significantly between conifers and broadleaves. The observed differences in forest floor C and N stocks were attributed to differences in litter turnover rates among the tree species. Mineral soil C stocks were significantly higher in stands of Norway spruce than in stands of oak and beech while...

  11. Isotope shifts in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations

    Energy Technology Data Exchange (ETDEWEB)

    Nazé, C.; Verdebout, S. [Service de Chimie Quantique et Photophysique, CP160/09, Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, B 1050 Brussels (Belgium); Rynkun, P.; Gaigalas, G. [Vilnius University, Institute of Theoretical Physics and Astronomy, LT-01108 Vilnius (Lithuania); Godefroid, M., E-mail: mrgodef@ulb.ac.be [Service de Chimie Quantique et Photophysique, CP160/09, Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, B 1050 Brussels (Belgium); Jönsson, P. [Group for Materials Science and Applied Mathematics, Malmö University, 205-06 Malmö (Sweden)

    2014-09-15

    Energy levels, normal and specific mass shift parameters as well as electronic densities at the nucleus are reported for numerous states along the beryllium, boron, carbon, and nitrogen isoelectronic sequences. Combined with nuclear data, these electronic parameters can be used to determine values of level and transition isotope shifts. The calculation of the electronic parameters is done using first-order perturbation theory with relativistic configuration interaction wavefunctions that account for valence, core–valence, and core–core correlation effects as zero-order functions. Results are compared with experimental and other theoretical values, when available.

  12. Stoichiometric deduction of activated sludge process for organic carbon and nitrogen removal

    Institute of Scientific and Technical Information of China (English)

    LIU Jian-yong; ZOU Lian-pei

    2009-01-01

    The activated sludge process (ASP) is the most generally applied biological wastewater treatment method. The ASP for the removal of organic carbon and nitrogen can be looked as the combination of eight processes. In order to set up an ASP model, the stoichiometric coefficients should be deduced so that the stoichiometric matrix can be presented. The important assumptions and simplifications behind the model for ASP are enumerated. Using the matrix, mass balance equation and consistent units, the stoichiometric coefficients in the eight processes are exclusively deduced one by one.

  13. Effects of nitrogen deposition on carbon cycle in terrestrial ecosystems of China

    DEFF Research Database (Denmark)

    Chen, Hao; Li, Dejun; Gurmesa, Geshere Abdisa

    2015-01-01

    Nitrogen (N) deposition in China has increased greatly, but the general impact of elevated N deposition on carbon (C) dynamics in Chinese terrestrial ecosystems is not well documented. In this study we used a meta-analysis method to compile 88 studies on the effects of N deposition C cycling...... and rate of N addition. Overall, our findings suggest that 1) decreased below-ground plant C pool may limit long-term soil C sequestration; and 2) it is better to treat N-rich and N-limited ecosystems differently in modeling effects of N deposition on ecosystem C cycle....

  14. Chlorophyll Fluorescence Emissions of Vegetation Canopies From High Resolution Field Reflectance Spectra

    Science.gov (United States)

    Middleton, E. M.; Corp, L. A.; Daughtry, C. S. T.; Campbell, P. K. Entcheva

    2006-01-01

    A two-year experiment was performed on corn (Zea mays L.) crops under nitrogen (N) fertilization regimes to examine the use of hyperspectral canopy reflectance information for estimating chlorophyll fluorescence (ChlF) and vegetation production. Fluorescence of foliage in the laboratory has proven more rigorous than reflectance for correlation to plant physiology. Especially useful are emissions produced from two stable red and far-red chlorophyll ChlF peaks centered at 685V10 nm and 735V5 nm. Methods have been developed elsewhere to extract steady state solar induced fluorescence (SF) from apparent reflectance of vegetation canopies/landscapes using the Fraunhofer Line Depth (FLD) principal. Our study utilized these methods in conjunction with field-acquired high spectral resolution canopy reflectance spectra obtained in 2004 and 2005 over corn crops, as part of an ongoing multi-year experiment at the USDA/Agriculture Research Service in Beltsville, MD. A spectroradiometer (ASD-FR Fieldspec Pro, Analytical Spectral Devices, Inc., Boulder, CO) was used to measure canopy radiances 1 m above plant canopies with a 22deg field of view and a 0deg nadir view zenith angle. Canopy and plant measurements were made at the R3 grain fill reproductive stage on 3-4 replicate N application plots provided seasonal inputs of 280, 140, 70, and 28 kg N/ha. Leaf level measurements were also made which included ChlF, photosynthesis, and leaf constituents (photosynthetic pigment, carbon (C), and N contents). Crop yields were determined at harvest. SIF intensities for ChlF were derived directly from canopy reflectance spectra in specific narrowband regions associated with atmospheric oxygen absorption features centered at 688 and 760 nm. The red/far-red S F ratio derived from these field reflectance spectra successfully discriminated foliar pigment levels (e.g., total chlorophyll, Chl) associated with N application rates in both corn crops. This canopy-level spectral ratio was also

  15. Effects of carbon dioxide and nitrogen on adhesive growth and expressions of E-cadherin and VEGF of human colon cancer cell CCL-228

    Institute of Scientific and Technical Information of China (English)

    Kai-Lin Cai; Guo-Bing Wang; Li-Juan Xiong

    2003-01-01

    AIM: To study the effects of carbon dioxide on the metastatic capability of cancer cells, and to compare them with that of nitrogen.METHODS: The colon cancer cell CCL-228 was treated with 100 % carbon dioxide or nitrogen at different time points and then cultured under normal condition. Twelve hours after the treatment, the survival rates of suspension cells and the expressions of e-cadherin and VEGF were examined.RESULTS: After 60 min of carbon dioxide and longer time of nitrogen treatment, the suspended cells increased and the expression of e-cadherin decreased while the expression of VEGF was enhanced significantly. And the effects of nitrogen were similar to, but weaker than, those of carbon dioxide.CONCLUSION: Carbon dioxide may improve the metastatic capability of cancer cells and its effects are significantly stronger than that of nitrogen. A sequential use of carbon dioxide and nitrogen in pneumoperitoneum may take the advantage of both gases.

  16. Long-term changes in forest carbon under temperature and nitrogen amendments in a temperate northern hardwood forest.

    Science.gov (United States)

    Savage, Kathleen E; Parton, William J; Davidson, Eric A; Trumbore, Susan E; Frey, Serita D

    2013-08-01

    Currently, forests in the northeastern United States are net sinks of atmospheric carbon. Under future climate change scenarios, the combined effects of climate change and nitrogen deposition on soil decomposition, aboveground processes, and the forest carbon balance remain unclear. We applied carbon stock, flux, and isotope data from field studies at the Harvard forest, Massachusetts, to the ForCent model, which integrates above- and belowground processes. The model was able to represent decadal-scale measurements in soil C stocks, mean residence times, fluxes, and responses to a warming and N addition experiment. The calibrated model then simulated the longer term impacts of warming and N deposition on the distribution of forest carbon stocks. For simulation to 2030, soil warming resulted in a loss of soil organic matter (SOM), decreased allocation to belowground biomass, and gain of aboveground carbon, primarily in large wood, with an overall small gain in total system carbon. Simulated nitrogen addition resulted in a small increase in belowground carbon pools, but a large increase in aboveground large wood pools, resulting in a substantial increase in total system carbon. Combined warming and nitrogen addition simulations showed a net gain in total system carbon, predominately in the aboveground carbon pools, but offset somewhat by losses in SOM. Hence, the impact of continuation of anthropogenic N deposition on the hardwood forests of the northeastern United States may exceed the impact of warming in terms of total ecosystem carbon stocks. However, it should be cautioned that these simulations do not include some climate-related processes, different responses from changing tree species composition. Despite uncertainties, this effort is among the first to use decadal-scale observations of soil carbon dynamics and results of multifactor manipulations to calibrate a model that can project integrated aboveground and belowground responses to nitrogen and climate

  17. Linking carbon-water- and nitrogen fluxes at forest ecosystems throughout Europe with a coupled soil-vegetation process model "LandscapeDNDC"

    Science.gov (United States)

    Molina Herrera, Saul; Grote, Rüdiger; Haas, Edwin; Kiese, Ralf; Butterbach-Bahl, Klaus

    2013-04-01

    Forest ecosystems in Europe play a key role in the emission reduction commitment agreed in the Kyoto Protocol for mitigating climatic change. Forest ecological functioning and potential services (such as carbon sequestration) are a matter of debate for policy decision makers resulting from the need of identifying affordable strategies for forest management and exploitation against climate change. Forest ecosystem functioning and the linkages governing carbon-, water- and nitrogen fluxes at site scale was evaluated for three dominant tree species (Pinus sylvestris, Picea abies and Fagus sylvatica) grown on 10 different sites across Europe. We did answer in particular the following questions: a) is LandscapeDNDC able to represent NEE, GPP, TER and ET fluxes for dominant forest types in Europe at different sites with only a species specific parameterization? b) What is the relation between carbon input into the ecosystem and on the emission of carbon and nitrogen from the forest soil? Furthermore we analyzed the interaction between carbon-, nitrogen-, and water cycle, in particular the dependence of gaseous fluxes on water and litter availability. LandscapeDNDC is a process based model that integrates modules for carbon, nitrogen and water cycling within terrestrial ecosystems (i.e. forest) on the site and regional scale. Biosphere, atmosphere and hydrosphere processes in forest ecosystems are linked by daily time step integration of the microclimate, water cycle, soil biogeochemistry and tree physiology and dimensional growth modules which balances all three aforementioned cycles. All processes and state variables are considered in a vertically structured one dimensional vertical column that reaches from rooting depth (more than 1 m depth) to the uppermost canopy layer. LandscapeDNDC was tested against long term (about 10 years) field data. The capability of the applied model for reproducing daily derived GPP and TER was accompanied by a high statistical precision (r

  18. Carbon cost of plant nitrogen acquisition: global carbon cycle impact from an improved plant nitrogen cycle in the Community Land Model.

    Science.gov (United States)

    Shi, Mingjie; Fisher, Joshua B; Brzostek, Edward R; Phillips, Richard P

    2016-03-01

    Plants typically expend a significant portion of their available carbon (C) on nutrient acquisition - C that could otherwise support growth. However, given that most global terrestrial biosphere models (TBMs) do not include the C cost of nutrient acquisition, these models fail to represent current and future constraints to the land C sink. Here, we integrated a plant productivity-optimized nutrient acquisition model - the Fixation and Uptake of Nitrogen Model - into one of the most widely used TBMs, the Community Land Model. Global plant nitrogen (N) uptake is dynamically simulated in the coupled model based on the C costs of N acquisition from mycorrhizal roots, nonmycorrhizal roots, N-fixing microbes, and retranslocation (from senescing leaves). We find that at the global scale, plants spend 2.4 Pg C yr(-1) to acquire 1.0 Pg N yr(-1) , and that the C cost of N acquisition leads to a downregulation of global net primary production (NPP) by 13%. Mycorrhizal uptake represented the dominant pathway by which N is acquired, accounting for ~66% of the N uptake by plants. Notably, roots associating with arbuscular mycorrhizal (AM) fungi - generally considered for their role in phosphorus (P) acquisition - are estimated to be the primary source of global plant N uptake owing to the dominance of AM-associated plants in mid- and low-latitude biomes. Overall, our coupled model improves the representations of NPP downregulation globally and generates spatially explicit patterns of belowground C allocation, soil N uptake, and N retranslocation at the global scale. Such model improvements are critical for predicting how plant responses to altered N availability (owing to N deposition, rising atmospheric CO2 , and warming temperatures) may impact the land C sink.

  19. Ultrahigh volumetric capacitance and cyclic stability of fluorine and nitrogen co-doped carbon microspheres

    Science.gov (United States)

    Zhou, Junshuang; Lian, Jie; Hou, Li; Zhang, Junchuan; Gou, Huiyang; Xia, Meirong; Zhao, Yufeng; Strobel, Timothy A.; Tao, Lu; Gao, Faming

    2015-09-01

    Highly porous nanostructures with large surface areas are typically employed for electrical double-layer capacitors to improve gravimetric energy storage capacity; however, high surface area carbon-based electrodes result in poor volumetric capacitance because of the low packing density of porous materials. Here, we demonstrate ultrahigh volumetric capacitance of 521 F cm-3 in aqueous electrolytes for non-porous carbon microsphere electrodes co-doped with fluorine and nitrogen synthesized by low-temperature solvothermal route, rivaling expensive RuO2 or MnO2 pseudo-capacitors. The new electrodes also exhibit excellent cyclic stability without capacitance loss after 10,000 cycles in both acidic and basic electrolytes at a high charge current of 5 A g-1. This work provides a new approach for designing high-performance electrodes with exceptional volumetric capacitance with high mass loadings and charge rates for long-lived electrochemical energy storage systems.

  20. Effect of biochar on leaching of organic carbon, nitrogen, and phosphorus from compost in bioretention systems.

    Science.gov (United States)

    Iqbal, Hamid; Garcia-Perez, Manuel; Flury, Markus

    2015-07-15

    Compost is used in bioretention systems to improve soil quality, water infiltration, and retention of contaminants. However, compost contains dissolved organic matter, nitrate, and phosphorus, all of which can leach out and potentially contaminate ground and surface waters. To reduce the leaching of nutrients and dissolved organic matter from compost, biochar may be mixed into the bioretention systems. Our objective was to test whether biochar and co-composted biochar mixed into mature compost can reduce the leaching of organic carbon, nitrogen, and phosphorus. There was no significant difference between the effects of biochar and co-composted biochar amendments on nutrient leaching. Further, biochar amendments did not significantly reduce the leaching of dissolved organic carbon, nitrate, and phosphorus as compared to the compost only treatment. The compost-sand mix was the most effective in reducing nitrate and phosphorus leaching among the media.

  1. High-performance oxygen reduction catalyst derived from porous, nitrogen-doped carbon nanosheets

    Science.gov (United States)

    Wang, Hao; Chen, Kai; Cao, Yingjie; Zhu, Juntong; Jiang, Yining; Feng, Lai; Dai, Xiao; Zou, Guifu

    2016-10-01

    A facile, self-foaming strategy is reported to synthesize porous, nitrogen-doped carbon nanosheets (N-CNSs) as a metal-free electrocatalyst for oxygen reduction reaction (ORR). Benefiting from the synergistic functions of N-induced active sites, a highly specific surface area and continuous structure, the optimal N-CNS catalyst exhibits Pt-like ORR activity (positive onset potential of ˜0 V versus Ag/AgCl and limiting current density of 5 mA cm-2) through a four-electron transfer process in alkaline media with excellent cycle stability and methanol tolerance. This work not only provides a promising metal-free ORR catalyst but also opens up a new path for designing carbon-based materials towards broad applications.

  2. Abundances in red giant stars - Nitrogen isotopes in carbon-rich molecular envelopes

    Science.gov (United States)

    Wannier, P. G.; Andersson, B.-G.; Olofsson, H.; Ukita, N.; Young, K.

    1991-01-01

    Results are presented of millimeter- and submillimeter-wave observations of HCN and HCCCN that were made of the circmustellar envelopes of eight carbon stars, including the two protoplanetary nebulae CRL 618 and CRL 2688. The observations yield a measure of the double ratio (N-14)(C-13)/(N-15)(C-12). Measured C-12/C-13 ratios are used to estimate the N-14/N-15 abundance ratio, with the resulting lower limits in all eight envelopes and possible direct determinations in two envelopes. The two determinations and four of the remaining six lower limits are found to be in excess of the terrestrial value of N-14/N-15 = 272, indicating an evolution of the nitrogen isotope ratio, which is consistent with stellar CNO processing. Observations of thermal SiO (v = 0, J = 2-1) emission show that the Si-29/Si-28 ratio can be determined in carbon stars, and further observations are indicated.

  3. Effect of species composition on carbon and nitrogen stocks in forest floor and mineral soil in Norway spruce and European beech mixed forests

    Science.gov (United States)

    Andivia, Enrique; Rolo, Víctor; Jonard, Mathieu; Formánek, Pavel; Ponette, Quentin

    2015-04-01

    Management of existing forests has been identified as the main strategy to enhance carbon sequestration and to mitigate the impact of climate change on forest ecosystems. In this direction, the conversion of Norway spruce monospecific stands into mixed stands by intermingling individuals of European beech is an ongoing trend in adaptive forest management strategies, especially in Central Europe. However, studies assessing the effect of changes in tree species composition on soil organic carbon (SOC) and nitrogen stocks are still scarce and there is a lack of scientific evidence supporting tree species selection as a feasible management option to mitigate the effects of predicted future climatic scenarios. We compared C and N stocks in the forest floor (litter and humus) and the top 10 cm of mineral soil in two monospecific stands of Norway spruce and European beech and in a mixed stand of both species. The effect of tree species composition on the C and N stocks and its spatial distribution was evaluated based on litterfall, root production, elevation and canopy opening, and by using a combination of modelling and geostatistical techniques. C stock was highest in the Norway spruce and the mixed stands, while N stock was highest in the mixed stand and lowest under European beech, with intermediate values in the Norway spruce stand. Each forest type showed differences in forest floor properties, suggesting that species composition is an important factor governing forest floor characteristics, including C and N stocks. The distribution of C and N stocks between forest soil layers was different for each forest type. C and N stocks were highest in the hummus layer under Norway spruce, whereas both stocks were lowest in the European beech stand. On the other hand, the mixed stand showed the highest C and N accumulation in the uppermost mineral soil layer, while the monospecific stands showed similar values. Litterfall was the main contribution to C and N stocks of the

  4. Stable carbon and nitrogen isotope signatures indicate recovery of marine biota from sewage pollution at Moa Point, New Zealand

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Karyne M

    2003-07-01

    Stable carbon and nitrogen isotopes have been used to assess sewage contamination of a sewage outfall, discharging milli-screened effluent into Moa Point Bay, New Zealand, and monitor the recovery of flora and fauna after the outfall's closure. An initial study characterising the extent of the discharge and the effects on seaweed (Ulva lactuca L.), blue mussels (Mytilus galloprovincialis) and limpets (Cellana denticulata) from the area, showed effects of the sewage discharge on flora and fauna were localised within in the bay. The immediate area surrounding the discharge area was found to contain limited biodiversity, with an abundance of Ulva lactuca, a bright green lettuce-like seaweed, typically found in areas with high nutrient input, limpets and small blue mussels. The nitrogen isotopic signature ({delta}{sup 15}N) is shown to be a good tracer of sewage pollution in seaweed and associated grazers (i.e. limpets) as a result of the increased contribution of urea and ammonia to seawater nitrogen derived from the effluent. The carbon isotopic signature ({delta}{sup 13}C) is suggested as a more appropriate sewage tracer for mussels, which filter feed the effluent's particulate organic matter from the water. Lower carbon:nitrogen ratios were found in Ulva lactuca sampled from around the outfall region compared to uncontaminated control sites. However carbon:nitrogen ratios do not vary significantly amongst shellfish species. After closure, monitoring continued for 9 months and showed that the carbon and nitrogen isotopic signatures of algae (Ulva lactuca L.) returned to similar control site levels within 3 months. Limpet and blue mussels (Cellana denticulata and Mytilus galloprovincialis) showed slower recovery times than the Ulva lactuca, with detectable levels of the sewage-derived carbon and nitrogen remaining in the animal's tissue for up to 9 months.

  5. XPS study and physico-chemical properties of nitrogen-enriched microporous activated carbon from high volatile bituminous coal

    Energy Technology Data Exchange (ETDEWEB)

    Robert Pietrzak [Adam Mickiewicz University, Poznan (Poland). Laboratory of Coal Chemistry and Technology

    2009-10-15

    N-enriched microporous active carbons of different physico-chemical parameters have been obtained from high volatile bituminous coal subjected to the processes of ammoxidation, carbonisation and activation in different sequences. Ammoxidation was performed by a mixture of ammonia and air at the ratio 1:3 (flow ratio 250 ml/min:750 ml/min) at 350{sup o}C, at each stage of production i.e. that of precursor, carbonisate and active carbon. Ammoxidation performed at the stage of demineralised coal or carbonisate has been shown to lead to a significant nitrogen enrichment and to have beneficial effect on the porous structure of the carbon during activation, allowing obtaining samples of the surface area of 2600-2800 m{sup 2}/g and pore volume 1.29-1.60 cm{sup 3}/g to be obtained with the yield of about 50%. The amount of nitrogen introduced into the carbon structure was found to depend on the sequence of the processes applied. The greatest amount of nitrogen was introduced for the processes in the sequence carbonisation {yields} activation {yields} ammoxidation. The introduction of nitrogen at the stage of active carbon leads to a reduction in the surface area and lowering of its sorption capacity. From the XPS study, ammoxidation introduces nitrogen mainly in the form of imines, amines, amides, N-5 and N-6, irrespective of the processing stage at which it is applied. 40 refs., 2 figs., 5 tabs.

  6. Modeling forest carbon and nitrogen cycles based on long term carbon stock field measurement in the Delaware River Basin

    Science.gov (United States)

    Xu, B.; Pan, Y.; McCullough, K.; Plante, A. F.; Birdsey, R.

    2015-12-01

    Process-based models are a powerful approach to test our understanding of biogeochemical processes, to extrapolate ground survey data from limited plots to the landscape scale and to simulate the effects of climate change, nitrogen deposition, elevated atmospheric CO2, increasing natural disturbances and land use change on ecological processes. However, in most studies, the models are calibrated using ground measurements from only a few sites, though they may be extrapolated to much larger areas. Estimation accuracy can be improved if the models are parameterized using long-term carbon stock data from multiple sites representative of the simulated region. In this study, vegetation biomass and soil carbon stocks, and changes in these stocks over a recent decade, were measured in 61 forested plots located in three small watersheds in the Delaware River Basin (DRB). On average, total vegetation biomass was 160.2 Mg C ha-1 and the soil carbon stock was 76.6 Mg C ha-1, measured during 2012-2014. The biomass carbon stock increased by 2.45 Mg C ha-1 yr-1 from 2001-2003 to 2012-2014. This dataset was subsequently used to parameterize the PnET-CN model at the individual plot basis, and averaged parameters among plots were then applied to generate new watershed-scale model parameters for each of the three watersheds. The parameterized model was further validated by the field measurements in each of the major forest types. The spatial distribution of forest carbon pools and fluxes in three watersheds were mapped based on the simulation results from the newly parameterized PnET-CN model. The model will also be run under different scenarios to test the effects of climate change, altered atmospheric composition, land use change, and their interactions within the three watersheds and across the whole DRB.

  7. The coupled effects of carbon and nitrogen on soil decomposition: A theoretical model

    Science.gov (United States)

    Darby, B.; Finzi, A.

    2013-12-01

    Soil organic matter (SOM) plays a crucial role in the carbon (C) cycle, holding 2.5 times more carbon than plant biomass. Ecosystem models predict that climate warming will stimulate decomposition of soil carbon stocks, in turn leading to positive feedbacks on warming. Recent empirical studies and modeling work has revealed the importance of microbial physiology and exoenzyme kinetics in driving SOM decomposition. Existing mathematical models describe the microbial processes and biophysics involved in the decomposition. However, although decomposition by nitrogen-degrading enzymes is included in some models, nitrogen (N) does not drive model behavior and there are no reaction kinetics associated with the depolymerization or uptake of N. Additionally, very few empirically measured kinetic values exist for N-degrading enzymes or the uptake of N by microbes. This study proposes a theoretical model of SOM decomposition based on the principles of exoenzyme kinetics and microbial biophysics that explicitly links C and N through microbial uptake and SOM decomposition kinetics and by placing stoichiometric constraints on microbial growth and exoenzyme production. After constructing the model framework, the model was then used to test soil-carbon responses to warming, and to explore the importance of N uptake and depolymerization kinetics in driving decomposition. The model predictions suggest that the response of kinetics to temperature are more important than microbial responses in determining decomposition rates. Additionally, variations in the kinetics of N depolymerization affected decomposition rates, whereas N uptake kinetics and their effect on enzyme production had almost no effect. The model outputs were also compared to a C-only model framework in order to assess the effects of N on model behavior. The incorporation of N into a SOM decomposition model produced different, and in some cases, contradictory results as compared to a C-only model. Overall, these

  8. Nitrogen and carbon assimilation by Saccharomyces cerevisiae during Sauvignon blanc juice fermentation.

    Science.gov (United States)

    Pinu, Farhana R; Edwards, Patrick J B; Gardner, Richard C; Villas-Boas, Silas G

    2014-12-01

    To investigate the assimilation and production of juice metabolites by Saccharomyces cerevisiae during winemaking, we compared the metabolite profiles of 63 Sauvignon blanc (SB) grape juices collected over five harvesting seasons from different locations of New Zealand before and after fermentation by the commercial wine yeast strain EC1118 at 15 °C. Metabolite profiles were obtained using gas chromatography-mass spectrometry and nuclear magnetic resonance and the oenological parameters were determined by Fourier transform infrared spectroscopy. Our results revealed that the amino acids threonine and serine were the most consumed organic nitrogen sources, while proline and gamma-aminobutyric acid were the least consumed amino acids during SB juice fermentation. Saccharomyces cerevisiae metabolised some uncommon nitrogen sources (e.g. norleucine, norvaline and pyroglutamic acid) and several organic acids, including some fatty acids, most likely after fermenting the main juice sugars (glucose, fructose and mannose). However, consumption showed large variation between juices and in some cases between seasons. Our study clearly shows that preferred nitrogen and carbon sources were consumed by S. cerevisiae EC1118 independent of the juice fine composition, whilst the consumption of other nutrient sources mainly depended on the concentration of other juice metabolites, which explains the uniqueness of each barrel of wine.

  9. One-step synthesis of nitrogen-iron coordinated carbon nanotube catalysts for oxygen reduction reaction

    Science.gov (United States)

    Choi, Woongchul; Yang, Gang; Kim, Suk Lae; Liu, Peng; Sue, Hung-Jue; Yu, Choongho

    2016-05-01

    Prohibitively expensive precious metal catalysts for oxygen reduction reaction (ORR) have been one of the major hurdles in a wide use of electrochemical cells. Recent significant efforts to develop precious metal free catalysts have resulted in excellent catalytic activities. However, complicated and time-consuming synthesis processes have negated the cost benefit. Moreover, detailed analysis about catalytically active sites and the role of each element in these high-performance catalysts containing nanomaterials for large surface areas are often lacking. Here we report a facile one-step synthesis method of nitrogen-iron coordinated carbon nanotube (CNT) catalysts without precious metals. Our catalysts show excellent long-term stability and onset ORR potential comparable to those of other precious metal free catalysts, and the maximum limiting current density from our catalysts is larger than that of the Pt-based catalysts. We carry out a series of synthesis and characterization experiments with/without iron and nitrogen in CNT, and identify that the coordination of nitrogen and iron in CNT plays a key role in achieving the excellent catalytic performances. We anticipate our one-step process could be used for mass production of precious metal free electrocatalysts for a wide range of electrochemical cells including fuel cells and metal-air batteries.

  10. Experimental Investigation of a Cryogenic Filter for Separating Solid Carbon Dioxide Particles from Liquid Nitrogen

    Institute of Scientific and Technical Information of China (English)

    LI Juan; SHI Yu-mei; WANG Rong-shun; LI Xiang-dong

    2009-01-01

    This paper presents an investigation of a new method of purifying cryogenic liquid using sintered metallic wire-mesh filter, which has the advantages of high purifying efficiency and preferred strength at absolutely low temperature. Experiments are conducted to purify solid CO2 particles from liquid nitrogen. Temperature and pressure in the upstream and downstream of the filter, and the flow rate of carbon dioxide (CO2) gas and liquid nitrogen are measured, with the gas content of filtrate analyzed using a CO2 concentration detector. It is illustrated that after filtration, the purity of liquid nitrogen (volume fraction) is higher than 99.99%, which means that the volume fraction of CO2 is less than 0.01%. Effects of operation parameters on the performance of the filter, such as pressure drop △p and filtration efficiency E are analyzed quantitatively. The present conclusions will provide a guideline to the optimumal design and operation of sintered metallic wire-mesh filter in cryogenic application.

  11. Application of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films for ultraviolet detection

    Science.gov (United States)

    Zkria, Abdelrahman; Gima, Hiroki; Yoshitake, Tsuyoshi

    2017-03-01

    Nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon (UNCD/a-C:H) films were grown by coaxial arc plasma deposition in the ambient of nitrogen and hydrogen mixed gases. Synthesized films were structurally investigated by X-ray photoemission and near-edge X-ray absorption fine structure spectroscopies. A heterojunction with p-type Si substrate was fabricated to study the ultraviolet photodetection properties of the film. Capacitance-voltage measurements assure the expansion of a depletion region into the film side. Current-voltage curves in the dark showed a good rectifying behaviour in the bias voltages range between ±5 V. Under 254 nm monochromatic light, the heterojunction shows a capability of deep ultraviolet light detection, which can be attribute to the existence of UNCD grains. As the diode was cooled from 300 K down to 150 K, the detectivity has a notable enhancement from 1.94 × 105 cm Hz1/2 W-1 at 300 K to 5.11 × 1010 cm Hz1/2 W-1 at 150 K, which is mainly due to a remarkable reduction in the leakage current at low temperatures. It was experimentally demonstrated that nitrogen-doped UNCD/a-C:H film works as ultraviolet-range photovoltaic material.

  12. 2D quasi-ordered nitrogen-enriched porous carbon nanohybrids for high energy density supercapacitors

    Science.gov (United States)

    Kan, Kan; Wang, Lei; Yu, Peng; Jiang, Baojiang; Shi, Keying; Fu, Honggang

    2016-05-01

    Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are intercalated into the interlayers of the expanded EG with the assistance of a vacuum. Subsequently, the intercalated aniline monomers could assemble on the interlayer surface of the expanded EG, accompanied by the in situ polymerization from aniline monomers to polyaniline. Meanwhile, the expanded EG could be exfoliated to graphite nanosheets. By subsequent pyrolysis and activation processes, the QNPC nanohybrids could be prepared. As supercapacitor electrodes, a typical QNPC12-700 sample derived from the precursor containing an EG content of 12%, with a high level of nitrogen doping of 5.22 at%, offers a high specific capacitance of 305.7 F g-1 (1 A g-1), excellent rate-capability and long-term stability. Notably, an extremely high energy density of 95.7 Wh kg-1 at a power density of 449.7 W kg-1 in an ionic liquid electrolyte can be achieved. The unique structural features and moderate heteroatom doping of the QNPC nanohybrids combines electrochemical double layer and faradaic capacitance contributions, which make these nanohybrids ideal candidates as electrode materials for high-performance energy storage devices.Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are

  13. Influence of temperature on carbon and nitrogen dynamics during in situ aeration of aged waste in simulated landfill bioreactors.

    Science.gov (United States)

    Tong, Huanhuan; Yin, Ke; Giannis, Apostolos; Ge, Liya; Wang, Jing-Yuan

    2015-09-01

    The effect of temperature on carbon and nitrogen compounds during in situ aeration of aged waste was investigated in lab-scale simulated landfill bioreactors at 35, 45 and 55 °C, respectively. The bioreactor operated at 55 °C presented the highest carbon mineralization rate in the initial stage, suggesting accelerated biodegradation rates under thermophilic conditions. The nitrogen speciation study indicated that organic nitrogen was the dominant species of total N in aerobic bioreactors due to ammonia removal. Leachate organic nitrogen was further fractionated to elucidate the fate of individual constituent. Detailed investigation revealed the higher bioconversion rates of N-humic and N-fulvic compounds compared to hydrophilic compounds in thermophilic conditions. At the end, waste material in 55 °C bioreactor was richer in highly matured humic substances (HS) verifying the high bioconversion rates.

  14. Optimal nitrogen and phosphorus codoping carbon dots towards white light-emitting device

    Science.gov (United States)

    Zhang, Feng; Wang, Yaling; Miao, Yanqin; He, Yuheng; Yang, Yongzhen; Liu, Xuguang

    2016-08-01

    Through a one-step fast microwave-assisted approach, nitrogen and phosphorus co-doped carbon dots (N,P-CDs) were synthesized using ammonium citrate (AC) as a carbon source and phosphates as additive reagent. Under the condition of an optimal reaction time of 140 s, the influence of additive with different N and P content on fluorescent performance of N,P-CDs was further explored. It was concluded that high nitrogen content and moderate phosphorus content are necessary for obtaining high quantum yield (QY) N,P-CDs, among which the TAP-CDs (CDs synthesized using ammonium phosphate as additive reagent) show high quantum yield (QY) of 62% and red-green-blue (RGB) spectral composition of 51.67%. Besides, the TAP-CDs exhibit satisfying thermal stability within 180 °C. By virtue of good optical and thermal properties of TAP-CDs, a white light-emitting device (LED) was fabricated by combining ultraviolet chip with TAP-CDs as phosphor. The white LED emits bright warm-white light with the CIE chromaticity coordinate of (0.38, 0.35) and the corresponding color temperature (CCT) of 4450 K, indicating the potential of TAP-CDs phosphor in white LED.

  15. Recently fixed carbon allocation in strawberry plants and concurrent inorganic nitrogen uptake through arbuscular mycorrhizal fungi.

    Science.gov (United States)

    Tomè, Elisabetta; Tagliavini, Massimo; Scandellari, Francesca

    2015-05-01

    Most crop species form a symbiotic association with arbuscular mycorrhizal (AM) fungi, receiving plant photosynthate and exchanging nutrients from the soil. The plant carbon (C) allocation to AM fungi and the nitrogen feedback are rarely studied together. In this study, a dual (13)CO2 and (15)NH4(15)NO3 pulse labeling experiment was carried out to determine the allocation of recent photosynthates to mycorrhizal hyphae and the translocation of N absorbed by hyphae to strawberry plants. Plants were grown in pots in which a 50 μm mesh net allowed the physical separation of the mycorrhizal hyphae from the roots in one portion of the pot. An inorganic source of (15)N was added to the hyphal compartment at the same time of the (13)CO2 pulse labeling. One and seven days after pulse labeling, the plants were destructively harvested and the amount of the recently fixed carbon (C) and of the absorbed N was determined. (13)C allocated to belowground organs such as roots and mycorrhizal hyphae accounted for an average of 10%, with 4.3% allocated to mycorrhizal hyphae within the first 24h after the pulse labeling. Mycorrhizae absorbed labeled inorganic nitrogen, of which almost 23% was retained in the fungal mycelium. The N uptake was linearly correlated with the (13)C fixed by the plants suggesting a positive correlation between a plant photosynthetic rate and the hyphal absorption capacity.

  16. The Implications of Growing Bioenergy Crops on Water Resources, Carbon and Nitrogen Dynamics

    Science.gov (United States)

    Jain, A. K.; Song, Y.; Kheshgi, H. S.; Landuyt, W.

    2015-12-01

    The bioenergy crops, Corn, Miscanthus and switchgrass have a potential to meet future energy demands in the US and mitigate climate change by partially replacing fossil fuels. However, the large-scale cultivation of these bioenergy crops may also impact climate change through changes in albedo, evapotranspiration (ET), and greenhouse gas (GHG) emissions. Whether these climate effects will mitigate or exacerbate climate change in the short and long terms is uncertain. The uncertainties come from our incomplete understanding of the effects of expanded bioenergy crop production on terrestrial water and energy balance, carbon and nitrogen dynamics, and their interactions. This study aims to understand the implications of growing large scale bioenergy crops on water resources, carbon and nitrogen dynamics in the United States using a data- modeling framework (ISAM) that we developed. Our study indicates that both Miscanthus and Cave-in-Rock switchgrass can attain high and stable yield over parts of the Midwest, however, this high production is attained at the cost of increased soil water loss as compared to current natural vegetation. Alamo switchgrass can attain high and stable yield in the southern US without significant influence on soil water quantity.

  17. Diet and mobility in Early Medieval Bavaria: a study of carbon and nitrogen stable isotopes.

    Science.gov (United States)

    Hakenbeck, Susanne; McManus, Ellen; Geisler, Hans; Grupe, Gisela; O'Connell, Tamsin

    2010-10-01

    This study investigates patterns of mobility in Early Medieval Bavaria through a combined study of diet and associated burial practice. Carbon and nitrogen isotope ratios were analyzed in human bone samples from the Late Roman cemetery of Klettham and from the Early Medieval cemeteries of Altenerding and Straubing-Bajuwarenstrasse. For dietary comparison, samples of faunal bone from one Late Roman and three Early Medieval settlement sites were also analyzed. The results indicate that the average diet was in keeping with a landlocked environment and fairly limited availability of freshwater or marine resources. The diet appears not to have changed significantly from the Late Roman to the Early Medieval period. However, in the population of Altenerding, there were significant differences in the diet of men and women, supporting a hypothesis of greater mobility among women. Furthermore, the isotopic evidence from dietary outliers is supported by "foreign" grave goods and practices, such as artificial skull modification. These results reveal the potential of carbon and nitrogen isotope analysis for questions regarding migration and mobility.

  18. Seasonal variation in stable carbon and nitrogen isotope values of bats reflect environmental baselines.

    Directory of Open Access Journals (Sweden)

    Ana G Popa-Lisseanu

    Full Text Available The stable carbon and nitrogen isotope composition of animal tissues is commonly used to trace wildlife diets and analyze food chains. Changes in an animal's isotopic values over time are generally assumed to indicate diet shifts or, less frequently, physiological changes. Although plant isotopic values are known to correlate with climatic seasonality, only a few studies restricted to aquatic environments have investigated whether temporal isotopic variation in consumers may also reflect environmental baselines through trophic propagation. We modeled the monthly variation in carbon and nitrogen isotope values in whole blood of four insectivorous bat species occupying different foraging niches in southern Spain. We found a common pattern of isotopic variation independent of feeding habits, with an overall change as large as or larger than one trophic step. Physiological changes related to reproduction or to fat deposition prior to hibernation had no effect on isotopic variation, but juvenile bats had higher δ13C and δ15N values than adults. Aridity was the factor that best explained isotopic variation: bat blood became enriched in both 13C and 15N after hotter and/or drier periods. Our study is the first to show that consumers in terrestrial ecosystems reflect seasonal environmental dynamics in their isotope values. We highlight the danger of misinterpreting stable isotope data when not accounting for seasonal isotopic baselines in food web studies. Understanding how environmental seasonality is integrated in animals' isotope values will be crucial for developing reliable methods to use stable isotopes as dietary tracers.

  19. Earth's early atmosphere as seen from carbon and nitrogen isotopic analysis of Archean sediments

    Science.gov (United States)

    Gibson, E. K., Jr.; Carr, L. P.; Gilmour, I.; Pillinger, C. T.

    1986-01-01

    The origin and evolution of the Earth's early atmosphere has long been a topic of great interest but determination of actual compositions over geologic time is a difficult problem. However, recent systematic studies of stromatolite deposits (Precambrian Paleobiology Research Group) has extended our knowledge of Archean ecosystems. It has been shown that many stromatolite deposits have undergone negligible alteration since their time of formation. The discovery of primary fluid inclusions within unaltered 3.5 b.y. old Archiean sediments and the observation that the 3.3 b.y. old Barberton cherts have remained closed to argon loss and have not been subjected to thermal metamorphism suggests that an opportunity exists for the direct measurement of the volatile constituents present at their time of formation. Of primary interest to this study was the possibility that the stromatolites and other Archean sediments might retain a vestige of the atmosphere and thus afford an indication of the variations in carbon dioxide and nitrogen isotopic compositions with time. A suite of essentially unaltered Archean stromatolites and the cherts of different ages and geologic sites have been analyzed for their trapped carbon dioxide and nitrogen compositions by the stepped combustion extraction tech nique utilizing static mass spectrometers for the isotope measurements.

  20. The potential of carbon and nitrogen isotopes to conservatively discriminate between subsoil sediment sources

    Science.gov (United States)

    Laceby, J. Patrick; Olley, Jon

    2013-04-01

    Moreton Bay, in South East Queensland, Australia, is a Ramsar wetland of international significance. A decline of the bay's ecosystem health has been primarily attributed to sediments and nutrients from catchment sources. Sediment budgets for three catchments indicated gully erosion dominates the supply of sediment in Knapp Creek and the Upper Bremer River whereas erosion from cultivated soils is the primary sediment source in Blackfellow Creek. Sediment tracing with fallout-radionuclides confirmed subsoil erosion processes dominate the supply of sediment in Knapp Creek and the Upper Bremer River whereas in Blackfellow Creek cultivated and subsoil sources contribute >90% of sediments. Other sediment properties are required to determine the relative sediment contributions of channel bank, gully and cultivated sources in these catchments. The potential of total organic carbon (TOC), total nitrogen (TN), and carbon and nitrogen stable isotopes (δ13C, δ15N) to conservatively discriminate between subsoil sediment sources is presented. The conservativeness of these sediment properties was examined through evaluating particle size variations in depth core soil samples and investigating whether they remain constant in source soils over two sampling occasions. Varying conservative behavior and source discrimination was observed. TN in the

  1. Synthesis and characterization of nitrogen-doped carbon nanotubes by pyrolysis of melamine

    Science.gov (United States)

    Li, Xuefei; Kong, Lingnan; Yang, Jinghai; Gao, Ming; Hu, Tingjing; Wu, Xingtong; Li, Ming

    2013-11-01

    The typical bamboo-like nitrogen doped carbon nanotubes (N-CNTs) have been successfully synthesized via pyrolysis of melamine (C3N6H6). The morphology of the samples is characterized by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The synthesized nanotubes are structurally uniform. The nitrogen to carbon atomic ratio of N-CNTs determined by chemical element analysis is found to be 0.23. The corresponding binding energy of the samples is obtained through X-ray photoelectron spectroscopy (XPS) and the characteristic infrared peaks are recorded by using Fourier transform infrared spectroscopy (FTIR). The characterization of thermal stability is obtained by thermo-gravimetric analysis (TGA) under flowing argon. The photoluminescence (PL) spectrum of the product shows that all the emission peaks are located in the blue-violet wavelength region, which indicates that N-CNTs may have potential applications in nano-optical device fields. Moreover, the growth mechanism of N-CNTs is carefully discussed.

  2. Electrocatalytic activity of nitrogen doped carbon nanotubes with different morphologies for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Chen Zhu; Higgins, Drew [Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada); Chen Zhongwei, E-mail: zhwchen@uwaterloo.c [Department of Chemical Engineering, Waterloo Institute for Nanotechnology, Waterloo Institute for Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada)

    2010-06-30

    Nitrogen doped carbon nanotubes (NCNTs) were synthesized by a single step chemical vapor deposition technique using either ferrocene or iron(II) phthalocyanine as catalyst and pyridine as the carbon and nitrogen precursor. Variations in surface morphology and electrocatalytic activity for oxygen reduction reaction (ORR) were observed between the NCNTs synthesized using different catalysts. The structural and chemical characterizations were carried out using transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrochemical activity of NCNTs was evaluated with rotating ring disc electrode (RRDE) voltammetry. Structural characterization suggested more defects formed on the NCNTs synthesized from ferrocene (Fc-NCNTs) which led to a rugged surface morphology compared to the NCNTs synthesized from iron(II) phthalocyanine (FePc-NCNTs). Based on the RRDE voltammetry study, Fc-NCNTs demonstrated much higher activity for ORR than FePc-NCNT. Evidences from the structural and chemical characterizations illustrate the potential impact of catalyst structure in shaping the surface structure of NCNTs and the positive effect of surface defects on ORR activity. These results showed that potential improvements on ORR activity of NCNTs could be achieved by tailoring the surface structure of NCNTs by using catalysts with different structures.

  3. Beyond carbon and nitrogen: guidelines for estimating three-dimensional isotopic niche space.

    Science.gov (United States)

    Rossman, Sam; Ostrom, Peggy H; Gordon, Forrest; Zipkin, Elise F

    2016-04-01

    Isotopic niche has typically been characterized through carbon and nitrogen ratios and most modeling approaches are limited to two dimensions. Yet, other stable isotopes can provide additional power to resolve questions associated with foraging, migration, dispersal and variations in resource use. The ellipse niche model was recently generalized to n-dimensions. We present an analogous methodology which incorporates variation across three stable dimensions to estimate the significant features of a population's isotopic niche space including: 1) niche volume (referred to as standard ellipsoid volume, SEV), 2) relative centroid location (CL), 3) shape and 4) area of overlap between multiple ellipsoids and 5) distance between two CLs. We conducted a simulation study showing the accuracy and precision of three dimensional niche models across a range of values. Importantly, the model correctly identifies differences in SEV and CL among populations, even with small sample sizes and in cases where the absolute values cannot precisely be recovered. We use these results to provide guidelines for sample size in conducting multivariate isotopic niche modeling. We demonstrate the utility of our approach with a case study of three bottlenose dolphin populations which appear to possess largely overlapping niches when analyzed with only carbon and nitrogen isotopes. Upon inclusion of sulfur, we see that the three dolphin ecotypes are in fact segregated on the basis of salinity and find the stable isotope niche of inshore bottlenose dolphins significantly larger than coastal and offshore populations.

  4. Nitrogen removal for low-carbon wastewater in reversed A~2/O process by regulation technology

    Institute of Scientific and Technical Information of China (English)

    张智; 陈杰云; 谢丽华; 范功端; 尹晓静; 李勇

    2009-01-01

    Full scale experimental study on nitrogen removal for low-carbon wastewater was conducted in reversed A2/O process in Jiguanshi waste water treatment plant in Chongqing,in order to aid the operation and maintenance of similar WWTP. When the proposed measures,such as using 0.1% (volume fraction of wastewater) landfill leachate,shortening HRT by 2/3 in the primary sedimentation tank and controlling DO at 0.5 mg/L in the 3rd section of aerobic zone,are applied,15% of the carbon source can be complemented,the favorable property of activated sludge is achieved,and the nitrogen removal effect is significantly improved. The effluent NH3-N is 2 mg/L and the removal rate is 90%. The effluent TN is 17 mg/L and the removal rate is 54%. The up-to-standard discharge of the effluent is achieved. And after the optimization,the unit electricity consumption also reaches 0.21 kW/h and saves 20%.

  5. Facile Synthesis of Nitrogen-doped Carbon Quantum Dots for Bio-imaging

    Directory of Open Access Journals (Sweden)

    de Yro Persia Ada N.

    2016-01-01

    Full Text Available Carbon quantum dots (CQD with fascinating properties has gradually become a rising star as a new nanocarbon member due to its nonthreatening, abundant and inexpensive nature. This study reports on a facile preparation of fluorescent carbon quantum dots (CQD from iota Carrageenan. CQD from iota Carrageenan was produced by hydrothermal method with a quantum yield (QY of 16 to 20%. Doping the CQD with nitrogen by the addition of tetraethylene pentamine (TEPE produced CQD with a QY of 77%. FTIR data confirmed the formation of hydroxyl, carboxylic and carbonyl functional groups as confirmed by the ToFSIMS data due to the presence of nitrogen bonds on the N-CQD produced with TEPE. The CQD and N-CQD produced are crystalline with graphitic structures because of the presence of sp2 graphitic d line spacing with the sizes ranging from 2 to 10nm. To examine the feasibility of using the CQD as nanoprobe in practical applications, labelling and detection of E.coli was performed. The E.coli fluoresced proving CQD as an effective probe in bio imaging application. This study has successfully demonstrated a facile approach of producing CQD with significant high quantum yields to fluorescent CQD for bio imaging applications.

  6. Adsorption/oxidation of sulfur-containing gases on nitrogen-doped activated carbon

    Directory of Open Access Journals (Sweden)

    Liu Qiang

    2016-01-01

    Full Text Available Coconut shell-based activated carbon (CAC was used for the removal of methyl mercaptan (MM. CAC was modified by urea impregnation and calcined at 450°C and 950°C. The desulfurization activity was determined in a fixed bed reactor under room temperature. The results showed that the methyl mercaptan adsorption/oxidation capacity of modified carbon caicined at 950°C is more than 3 times the capacity of original samples. On the other hand, the modified carbon caicined at 950°C also has a high capacity for the simultaneous adsorption/oxidation of methyl mercaptan and hydrogen sulfide.The introduce of basic nitrogen groups siginificantly increases the desulfurization since it can facilitate the electron transfer process between sulfur and oxygen. The structure and chemical properties are characterized using Boehm titration, N2 adsorption-desorption method, thermal analysis and elemental analysis. The results showed that the major oxidation products were dimethyl disulfide and methanesulfonic acid which adsorbed in the activated carbon.

  7. Nitrogen-enriched carbon sheets derived from egg white by using expanded perlite template and its high-performance supercapacitors

    Science.gov (United States)

    Chen, Jiucun; Liu, Yinqin; Li, Wenjun; Xu, Liqun; Yang, Huan; Li, Chang Ming

    2015-08-01

    Nitrogen-enriched carbon sheets were synthesized using egg white as a unique carbon source and expanded perlite as a novel template. The as-prepared material was further used as an electrode material for supercapacitor applications, demonstrating excellent supercapacitance with a maximum gravimetric specific capacitance of 302 F g-1 at 0.5 A g-1 in a 3-electrode setup for a sample carbonized at 850 °C and activated for 6 h. Moreover, the carbon sheet-based capacitor with 2-symmetric electrodes showed an excellent cycle life (2% loss at 0.1 A g-1 after 10 000 cycles). The excellent performance may be attributed to the combination of the 3D carbon structure and the highly concentrated doped nitrogen component from the natural egg source for superior pseudocapacitance.

  8. Stable isotopes of helium, nitrogen and carbon in a coastal submarine hydrothermal system

    Science.gov (United States)

    Vidal, Francisco V.; Welhan, John; Vidal, Victor M. V.

    1982-03-01

    Geothermal gases from submarine and subaerial hot springs in Ensenada, Baja California Norte, Mexico, were sampled for determination of gas chemistry and helium, nitrogen and stable carbon isotope composition. The submarine hot spring gas is primarily nitrogen (56.1% by volume) and methane (43.5% by volume), whereas nearby subaerial hot spring gases are predominantly nitrogen (95-99% by volume). The N 2/Ar ratios and σ 15N values of the subaerial hot spring gas indicate that it is atmospheric air, depleted in oxygen and enriched in helium. The submarine hot spring gas is most probably derived from marine sediments of Cretaceous age rich in organic matter. CH 4 is a major component of the gas mixture ( σ 13C = -44.05% 0), with only minor amounts of CO 2 ( σ13C= -10.46% 0). The σ 15N of N 2 is + 0.2% 0 with a very high N 2/Ar ratio of 160. The calculated isotopic equilibra tion temperature for CH 4CO 2 carbon exchange at depth in the Punta Banda submarine geothermal field is approximately 200°C in agreement with other geothermometry estimates. The 3He/ 4He ratios of the hot spring gases range from 0.3 to 0.6 times the atmospheric ratio, indicating that helium is predominantly derived from the radioactive decay of U and Th within the continental crust. Thus, not all submarine hydrothermal systems are effective vehicles for mantle degassing of primordial helium.

  9. Valuing multiple eelgrass ecosystem services in Sweden: fish production and uptake of carbon and nitrogen

    Directory of Open Access Journals (Sweden)

    Scott Glenn Cole

    2016-01-01

    Full Text Available Valuing nature’s benefits in monetary terms is necessary for policy-makers facing trade-offs in how to spend limited financial resources on environmental protection. We provide information to assess trade-offs associated with the management of seagrass beds, which provide a number of ecosystem services, but are presently impacted by many stressors. We develop an interdisciplinary framework for valuing multiple ecosystem services and apply it to the case of eelgrass (Zostera marina, a dominant seagrass species in the northern hemisphere. We identify and quantify links between three eelgrass functions (habitat for fish, carbon and nitrogen uptake and economic goods in Sweden, quantify these using ecological endpoints, estimate the marginal average value of the impact of losing one hectare of eelgrass along the Swedish northwest coast on welfare in monetary terms, and aggregate these values while considering double-counting. Over a 20 to 50 year period we find that compa